March 14, 2012


The interplay of exercise and ketosis – Part II

by Peter Attia

Read Time 10 minutes

You’ll recall from last week’s post I did a self-experiment to see if I could learn something about the interplay of exercise and ketosis, at least in myself. To understand this discussion, you’ll want to have read Part I of this post.

However, before getting to this, I want to digress and briefly address two unrelated issues:

  1. Some of you (about 67 or 68 as of this writing) have sent me various links to news reports released yesterday reporting on a study out of Harvard’s School of Public Health.  I was planning to eventually write a post about how observational epidemiology is effectively at the heart of the nutritional crises we face – virtually every nutrition-based recommendation (e.g., eat fiber, don’t eat fat, salt is bad for you, red meat is bad for you) we hear is based on this sort of work.  Given this study, and the press it’s getting, I will be writing the post on observational epidemiology next weekHowever, I’m going to ask you all to undertake a little “homework assignment.”  Before next week I would suggest you read this article by Gary Taubes from the New York Times Magazine in 2007 which deals with this exact problem.
  2. I confirmed this week that someone (i.e., me) can actually eat too much of my wife’s ice cream (recipe already posted herepretty please with lard on top no more requests for it).  On two consecutive nights I ate about 4 or 5 bowls of the stuff.  Holy cow did I feel like hell for a few hours.  The amazing part is that I did this on two consecutive nights.  Talk about addictive potential.  Don’t say I didn’t warn you…

OK, back to the purpose of this post: How is ketosis impacting my ability to exercise? Here is the summary of the results from my personal experiment:


Exercise summary data

Let’s take a closer look at what may have been going on in each workout and see what we can learn.



This workout probably produced the most lactate of the three workouts (we don’t know for sure because I only measured immediate pre- and post- levels without measuring in-workout levels).  My glucose level rose by nearly 40% during this workout despite the fact that I did not consume anything.

How does this happen?  Our bodies store glucose in the liver and in muscles in a “storage” form (a long chain of joined glucose molecules) called glycogen.

Whenever our bodies cannot access sufficient cellular oxygen, our metabolism shifts to a less efficient form of energy acquisition called anaerobic catabolism.   During these periods of activity, we cannot oxidize fat or glycogen (i.e., use oxygen to harness the full chemical potential of fat or carbohydrate molecules).  I will be writing in much more detail about these ideas in the next month or so, so don’t worry if these ideas seem a bit foreign right now.  Just know that sometimes our bodies can convert fat or glucose to energy (efficiently), and sometimes we can only convert glucose to energy (inefficiently).

Because of my ketosis, and the metabolic flexibility that accompanies it, I only “require” that my body turn to glucose for energy under the most “stressful” forms of exercise – like I was doing a lot of during this workout.  But keep in mind, my muscles CANNOT export one gram of the glucose they store, so any glucose in my bloodstream is either ingested (which I didn’t do) or coming from my liver, which CAN export glucose.

Furthermore, the stress of a workout like this results in my adrenal glands releasing a set of chemicals called catecholamines, which cause my liver to export even more of its stored glucose via a process called hepatic glucose output (HGO).

[As an aside, one of the major defects in type-2 diabetes is the inability of insulin to suppress HGO.  In other words, even when not under the catecholamine stress that “should” lead to HGO, their livers constantly export glucose, which contributes to elevated blood glucose levels.  The very popular drug, metformin, used often in type-2 diabetes, blocks this process.]

While I did experience a pretty large rise in lactate (almost 3x), my ketones still went up a bit.  This could imply a few things:

  • Elevated lactate levels do not directly inhibit beta-hydroxybutyrate (B-OHB)
  • Mild elevations in glucose do not directly inhibit B-OHB
  • Mild elevations in glucose do not directly inhibit B-OHB, if insulin is being suppressed (as is the case during vigorous exercise)
  • B-OHB was suppressed, but we are only appreciating the net effect, which was a small increase (i.e., because of my MCT oil and activity, B-OHB levels were rising dramatically, but the rise was blunted by some other factor, such as HGO, insulin, and/or lactate)

More questions than answers from this workout, so on to the next workout.



Despite this being a tough ride at several points, on average it was less stressful than the other two workouts and I spent the greater fraction of time in my aerobic to tempo (zone 2 to zone 3) zones.

A ride like this, however, is a great example of the advantages of improved metabolic flexibility that accompanies nutritional ketosis.  My average heart rate during this 6 hour ride was 141.  Prior to becoming ketotic, at a HR of 141 my respiratory quotient (RQ) was about 0.98, which meant I was almost 100% dependent on glycogen (glucose) for energy.  Today, at a HR of 141 (with the same power output), my RQ is about 0.7 to 0.75, which means at the same HR and same power output as prior to ketosis, I now rely on glycogen for only about 10% of my energy needs, and the remaining 90% comes from access to my internal fat stores.

This is an important point.  I will devote future posts to this topic in more detail, but I wanted to use this opportunity to mention it.

So what happened physiologically on this ride?

  • My glucose levels fell, probably because I was slowly accessing glycogen stores for peak efforts (once my HR reaches 162 I become 50% dependent on glycogen) throughout the ride (e.g., peak climbing efforts, hard sections on flats), but my liver was not “called on” to dump out a massive amount of glucose in response to a catecholamine surge (and if it was, at some point during the ride, that amount of glucose had been used up by the time I was finished).
  • B-OHB levels increased by about 2.5x – to 4.4. mM, which is pretty high for me.  My highest recorded B-OHB level was 5.1 mM (also after a long ride).  This confirms what my RQ data indicate — my body almost entirely relies on fat oxidation for energy for activity at this intensity.  In the process, B-OHB is generated in large quantities, both for my brain and also my skeletal muscles (e.g., leg muscles). In reality, cardiac myocytes (heart muscle cells) also “like” B-OHB more than glucose and probably also access it when it is abundant.
  • Lactate levels by the end of the ride were effectively unchanged though. Based on “feel,” I suspect I hit peak lactate levels of 8 to 10 mM on this ride during peak efforts, but I had ample time to clear it.

A few observations:

  • I consumed 67 gm of carbohydrate on this ride (of which 50 gm was Generation UCAN’s super starch), yet this did not appear to negatively impact my ability to generate ketones.  Technically, we can’t be sure this is the case, since I would have needed a “control” to know this (e.g., my metabolic and genetic twin doing and eating everything the same as I did, but without the consumption of super starch and/or without the bike ride).  It’s possible that super starch did slightly inhibit ketosis and that my B-OHB level would have been, say, 5.0 mM instead of 4.4 mM.  Metabolic studies of super starch show that it has a minimal impact on insulin secretion and blood glucose levels, hence the name “super” starch.
  • Whatever impact peak levels of lactate production and hepatic glucose output had during the ride, they seem blunted by the end of the ride (and the ride did finish with a modestly difficult 1.4 mile climb at 6-7% grade, which I rode at a HR of about 150).

Since neither lactate levels nor glucose levels (nor insulin levels by extension) were elevated, I can’t really draw any conclusion about whether one factor, more than any other, suppressed production of B-OHB, so on to the next workout.


High intensity training

This sort of workout spans the creatine-phosphate (CP) system and the anaerobic energy system, and probably involves the aerobic energy system the least. I’ll write a lot about these later, but for now just know the CP system is good for very short bursts of energy (say 10-20 seconds) and recall the previous discussion of aerobic and anaerobic catabolism.  In other words, this is the type of workout where my nutritional state of ketosis offers the least advantage.

  • This workout saw the greatest increase in glucose level, about 70%.  It is important to recall that during this workout I ingested water with a small amount of branched chain amino acids (BCAA’s – valine, leucine, isoleucine) and super starch, about 4 gm and 10 gm, respectively. I do not believe either accounted for the sharp rise in blood glucose and, again, I believe hepatic glucose output in response to a strong catecholamine surge attributed to this increase.
  • Lactate levels also rose, though probably less so than during a peak swim effort.  This suggests more of the effort in this workout was fueled by the CP system (versus the anaerobic system, which probably played a larger role in the swim workout).
  • This was the only workout that saw a fall in B-OHB levels, which now offers some insight into what might be impacting B-OHB production.

Contrasting this workout with the swim workout draws a pleasant contrast: both saw a similar rise in lactate, but one saw twice the rise in blood glucose.  In the former, B-OHB was unchanged (actually rose slightly), while in the latter, B-OHB fell by over a third.

This suggests – but certainly does not prove – that it is not lactate per se that inhibits ketone (B-OHB) production, but rather glucose and/or insulin.  It is possible the BCAA played a role, and if I was thinking straight, I would not have consumed anything during this workout to remove variables. But I have a very hard time believing 3 or 4 gm of BCAA could suppress B-OHB. When you see hoof prints in the sand, you should probably think of horses before you think of zebras.

Conversely, there is some evidence that lactate promotes re-esterification of fatty acids into triglycerides within adipose cells.  What does that mean in English? High levels of lactate take free fatty acids and help promote putting them back into storage form.  This would prevent free fatty acids from making their way to the liver where they could be turned into ketones (e.g., B-OHB). In other words, we may be missing this effect because of my sampling error – I only sampled twice per workout, rather than multiple times throughout the workout.


So what did I learn, overall?

I think it’s safe to say I did not definitively answer any questions, which is not surprising given the number of confounding factors, lack of controls, and sample size of one.  However, I think I did learn a few things.


Lesson 1

The metabolic advantages of nutritional ketosis seemed most apparent during my bike ride, evidenced by my ability to access internal fat stores across a much broader range of physiologic stress than a non-ketotic individual.  (More on this in Lesson 4.)


Lesson 2

The swim and high intensity dry-land workouts suggested that my state of nutritional ketosis did not completely impair my ability to store or export hepatic glucose.  This is a very important point!  Why?  Because, it runs counter to the “conventional wisdom” of low-carb (or ketotic) nutrition with respect to physical performance.  We are “told” that without carbohydrates we can’t synthesize glycogen (i.e., we can’t store glucose).  However, those who promote this idea fail to realize that glycerol (the backbone of triglycerides) is turned into glycogen, along with amino acids, not to mention the 20 to 40 gm of carbohydrates I consume each day (since my brain doesn’t need them).  We know muscles still store glycogen in ketosis, as this has been well studied and documented via muscle biopsies by Phinney, Volek, and others.  But, my little self-experiment actually adds a layer to this.  Because muscle can’t export glucose (muscle lacks the enzyme glucose-1-phosphatase), we know that the increase in my blood glucose was accounted for by HGO – my liver exporting its glycogen.  In other words, ketosis does not appear to completely impair hepatic glycogen formation or export.  Again, we’d need controls to try to assess how much, if any, hepatic glycogen formation and/or export is inhibited.  It’s hard to make the argument that being in ketosis is allowing me to swim and do high intensity training with greater aptitude, and as I’ve commented in the past, I feel I’m about 5-10% “off” where I was prior to ketosis for these specific activities, but at the same time, I could be doing more to optimize around them (e.g., spend less time on my bike which invariably detracts from them, supplement with creatine which may support shorter, more explosive movements), which I am not.


Lesson 3

Consuming “massive” amounts of super starch (50 gm on the ride), did not seem to adversely affect my ketotic state.  My total carbohydrate intake for that day, including what I consumed for the other 18 hours of the day, was probably close to 90 gm (50 gm of super starch plus 40 gm of carbs from the other food I ate).  This suggests one or two possibilities:

  • Because of the molecular structure of super starch (I’ll be discussing this in the future, so please hold questions) and the concomitant metabolic profile that follows from this structure, it may not inhibit ketosis like other carbohydrate, and/or
  • During periods of profound physical stress insulin secretion is being sufficiently inhibited that higher-than-normal amounts of carbohydrate can be tolerated without negatively impacting ketone production.

This is pretty straightforward to test, even in myself.  I just haven’t done so yet.


Lesson 4

While it’s probably the case that my liver has less glycogen (i.e., stored glucose) at any point in time, relative to what would be present if I were eating a high-carb diet, it’s not clear this matters, at least for some types of workouts.  Why? Take the following example:

  • Someone my size can probably store about 100 gm of hepatic (liver) glycogen and about 300 gm of muscle glycogen at “full” capacity. This represents about 1600 calories worth of glucose – the most I can store at any one time.
  • Before I was ketotic, my RQ at 60% max VO2 (about 2,500 mL of O2 per min consumption) was nearly 1.00, so at that level of power output (a pace I can hold for hours from a cardiovascular fitness standpoint) I required 95% of my energy to come from glycogen.  So, how long do my glycogen stores last?  2,500 mL of O2 per minute translates to about 750 calories per hour, so I would be good for about 2 hours and 15 minutes on my glycogen stores.
  • Contrast this with my ketotic state.  Let’s assume my glycogen stores are now only half what they were before.  Muscle biopsy data suggests this is probably an overly conservative estimate, but let us assume this to be the case. Now I only store 50 mg of hepatic glycogen and 150 gm of muscle glycogen, about 800 calories worth of glucose.
  • In ketosis, my RQ at 60% max VO2 is 0.77 (at last check), telling me I am getting only 22% of my energy from glucose and the remaining 78% from fat.  So, how long do my depleted glycogen stores last? Nearly 5 hours.  Why?  Because I barely access glucose at the SAME level of oxygen consumption and the same power output. 

I know what you’re thinking…why is this an advantage? Just consume more glucose as you ride! It’s not that simple, but you’ll have to wait until my upcoming post, “What does exercise have to do with being in the ICU” to find out.

Going back to the black sheep example I open Part I of this post with, we know that at least one person in nutritional ketosis seems to make enough liver and muscle glycogen to support even the most demanding of his energetic needs.


Photo by Troy Oldham on Unsplash

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  • Doc,

    I can do all the cardio I want without problem, but when I add weightlifting (being mindful to only do it a couple of times per week, not over-doing it, etc.), I ‘hit a wall’ and feel run down. Any idea why this would be? I’ve reached my goal weight, and am very active, but I’d love to add some more muscle but not if lifting weights is going to make me feel like garbage again : (


    • Mark, it definitely took me a while to get my “juice” back in the weight room once eliminating carbs. Over 12 weeks. In reality, I am probably 5-10% weaker now than I was on a “normal” carb diet. For me the tradeoff is worth it, but it might not be for you. That said, I think you may need more time to adapt. Also, you need to make sure you’ve got all the other variables tweaked (e.g., sodium, potassium, magnesium, BCAA, glutamine).

    • Dan

      So is bad for a type2 diabetic to do HIIT?

  • Thank you so much for this and all your other posts! So wonderful to have somebody actually providing the science behind the Carbohydrate hypothesis in a blog form (I’m looking at your Mr. Taubes! 😉 )

    I exercise constantly, and one of the questions I am constantly asked is, “Don’t I need to supplement with some Carbs?” I generally don’t know. I know there are diets offered by Lyle McDonald called the “Targeted Ketogenic Diet” and “Cyclic Ketogenic Diet” or TKD and CKD respectively. However, McDonald has generally dismissed the science offered up by Mr. Taubes which I find run directly counter to the very things McDonald espouses.

    As Mark posted earlier, I sometimes hit a wall a little earlier when lifting heavy weights while trying to stay in ketosis, which I would be able to push through with some carbs previously. However, I still continue to gain strength and muscle mass, because I eat when I am hungry until I am full.

    The one thing i wonder about is whether it is possible to gain weight while eating lo-carb and what is the mechanism? Does it essentially have to be an insulin response via Gluconeogenesis?

    • Try experimenting with creatine for 4-week cycle? You can definitely gain weight weight eating low carb (I’m assuming you mean lean mass), but it is a bit tougher in low insulin environment. Remember, insulin is an anabolic hormone.

  • Mike H

    It seems like from your experience and from what Steve Phinney’s studies show, ketosis is the optimal state for an endurance athlete. Any idea if this type of diet has been adopted by a significant number of professional triathletes/marathoners/cyclists? Phinney is also big on never breaking ketosis, so no nonsense like carb cycling or carb loading. Do you agree with this?

    • I think the perfect athletic event for ketosis would be an Ironman triathlon or marathon running or ultramarathoning. Anyone who needs to be *just* under threshold for really long periods of time will capture most of the benefits of ketosis. But in my experience (and I believe Steve’s), do you have to give up some sprint capacity, so I would not recommend it even for the guy trying to win the Tour de France, as you still need to sprint when the pack moves.
      Carb cycling does not make sense if your goal is to really optimizing your body around ketosis. Perhaps it has benefits for other reasons.

    • greensleeves

      Proof of this can be readily found in vocal low-carb advocate, the Swedish champion Jonas Colting:

    • Dave

      Can’t you work around the sprint capacity issue by doing occasional carb refeeding? That’s what I do. I am very low carb during the week for marathon training, and will eat more carbs for my long runs and occasionally carb up for speed training. Am I still going to lack spring capacity on race day even if I’m carbed up?

      • I could, but it would mean going into and out of ketosis constantly. Also, the carbs would take away from my sub-threshold performance. It’s all a trade-off. No “right” way to do it. I’ll keep fiddling with it over time.

    • First, I’ll admit I’m really new to the notion of MET (Seebohar) and Ketosis based endurance training. I just stumbled on this site, but have been reading and working on following Bob’s work for a couple months now. I haven’t tested myself to the level that Peter has, but I am definitely convinced that this is a good model for me. And I am an Ironman, Ultramarathon, and long distance solo cyclist.

      In reply to Peter’s comment about Ironman, Marathons, and Ultramarathons being the “perfect athletic event for ketosis”… I would take one small exception with Peter’s suggestion that Ketosis is ideal for Marathons… specifically “elite” Marathon runners, here’s why:

      At the current world class marathon times of 2:05:00-ish, I think we are really seeing a breakthrough in the pace and timing of (world class) marathons where they can realistically be completed at essentially near-AT pace ~RQ in the >0.8…>0.9 zone. I haven’t run the math on this, and so Peter may have a lot more data and numbers to disprove my assumption. But my instinct tells me that these world class runners are actually running for a short enough duration of time that they can fuel almost entirely off of the calories available in their muscle and liver glycogen stores. Consider that a 130lbs runner will only require about 2200 calories to run at 5 min/miles for 2 hours.

      Of course I totally agree that for mere mortals who are going to run 3+ hour marathons, or more like 4+ hour marthons, then Ketosis or near-Ketosis is a far more preferable metabolic “mode” to race in.

      Anyway… like I said, I just found this site, but so far, I’m loving everything I’m reading. Great stuff!

  • Greg


    Thanks for this excellent post. I used to scour books searching for a reasonably clear explanation of energy transport during various phases of exercise as a long-distance runner. It seemed as if most authors merely parrot the same series of unexamined and rather unexplained literature on the subject. I feel like I have a better feel for energy transport systems after this post, not just from the standpoint of being in a ketotic state (which I’m not…I’m low carb, but haven’t taken the final plunge), but just in general.

    An interesting take-away as a former marathoner is your pre and post ketotic energy transfer as it related to your aerobic cycling data. Think “hitting the wall” in terms of the 2 hr and 15 min store of glycogen pre-ketotic and then the post-ketotic 5 hrs +.

    One thought that comes to mind. Not that I care about race performance anymore (I’m not out for a gold medal or anything close, just my health), but could one selectively use simple carbs for a race event in order to maximize performance without any change to the ketotic state?— or, if not fully ketotic (like me), in any case avoid the ill effects of carb’s in general, such as insulin production. In other words, like the endurance athlete drinking a few cups of coffee, could hitting some carbs on race day be beneficial without ill effects if you merely see them as a sports supplement? I realize that you use UCAN (which I plan on trying myself), but it comes to mind, why bother?–why not use any simple carb if your metabolic system is already suppressing insulin in the midst of an endurance activity.

    Again, great blog and information. By the way, my wife and I made the ice cream and we are addicted.


    • Greg, if my goal were to win a gold medal I would probably have to change my diet. If you think about it (I’ll be doing an entire post on this), carbohydrates are in some ways like a performance enhancing drug — help with certain aspects of performance, but have some chronic harm associated with use.

      UCAN offers many advantages over, say, fructose, glucose, or maltodextrin. I’ll write about this at some point, also.

    • Michael

      Peter, I would love to see the article comparing carbs to performance enhancing drugs! One thing that has always bugged me is when people say that our bodies must prefer (be designed for) carbs since we use those first for energy. The other option is that those carbs are seen as toxic by the body and are used first just to get rid of them. Fat could still be the preferred energy source.

  • Elenor

    “When you see hoof prints in the sand, you should probably think of horses before you think of zebras.”

    Unless you’re in Africa.

    (Fantastic entry/entries! I’m SO glad you’re doing — and reporting! — these great N=1 experiments. Thank you for your blog!)

  • Neil

    Great post.

    Is there any value then in trying to deplete glycogen as much as possible via weight training or some other means to improve insulin sensitivity? I, for one, was very surprised at how much glycogen the body can store even when in ketosis.

    • Neil, I can’t think of one off hand, except that it would allow you to ingest more carbs later to replace glycogen stores (vs. de novo lipogensis). Of course, this would need to be balanced against the downside of having very low glycogen levels.

    • Carlo

      Wouldn’t this be a good way to get “into” ketosis quicker?

    • Neil

      I was just wondering how long that would take.

  • Hey Peter, as usual great post…I think actually reading it as I had just read J. Stanton’s post debunking the aforementioned Harvard study (which I highly recommend reading for anyone on the insulin hypothesis side of the debate, or anyone, for that matter) it’s going to take a further retreading to completely absorb, but, eh, something for after my nap.
    Oh, and as far as the topic of losing some strength in the gym and sprint speed through being ketogenic: I absolutely refuse to believe that our fore bearer’s ability to outrun a sabretooth or out wrestle a grizzly would be predicated upon them having recently consumed some berries or something, there must be some piece of the puzzle that we’re missing. Mmmm, berries. Oh, and I find the reaction to the ice creamer recipe amusing…you really should just edit your previous post to include it in the body, I mean, low carb ice cream to an audience of, mostly, die hard low carbers (who’re therefore largely self selected for being carbohydrate addicts), that’s just chumming the waters, lol.

  • Edmund Brown
  • Marilyn

    Thanks for the link to the 2007 Taubes article! Although I frequently google his name to see what’s new, I had somehow missed that one.

    • This one is a gem. One could make an argument it’s even more important than all the others.

  • Tim

    “Today, at a HR of 141 (with the same power output), my RQ is about 0.7 to 0.75, which means at the same HR and same power output as prior to ketosismes from access to my internal fat stores.” Guessing due to your weight loss your weight to power output actually increased. In addition to vo2 testing, any testing done on your ftp- if your familiar with that.

    • Between two tests FTP actually went up a touch from loss of 6 pounds, I think. Not much, though.

  • Larry Candell

    Thanks for assembling so much interesting information in such a useful way. In your interpretation of your latest experiment, I wonder what role you think that gluconeogenesis plays in the glucose levels you measure. I would imagine that your hepatic glycogen stores could be much lower than you estimate, and instead that your liver is actually manufacturing glucose to meet your body’s needs. Under this scenario, your capacity to exercise would be rate limited by how fast you can break down amino acids and lactate to form glucose, not a finite store of glycogen in the liver. The path to ketosis involves depleting the liver glycogen stores. Is there some experiment you can imagine that would validate that your hepatic glycogen levels get restored while in ketosis?

    • Yes, this is also a possible explanation. My guess, if I had to make one, would be a bit of these, but still primarily HGO for this workout. Given how short this workout is, I think contribution from the Cori Cycle (lactate) and amino acid breakdown would not account for much of the rise I saw. BUT, we can’t know without testing this! This actually would not be difficult to indirectly test (i.e., without a liver biopsy, which would be an unjustifiable risk in my opinion) using labeled glucose. Great point.

  • Martin

    Peter, I used to be in the same category as you: lots of activity, endurance sports (marathons, mountainbiking) and rock-climbing. I worked out a lot and stayed lean and fit till about 30. Then with every year I’d get fatter even though I tried to work out even harder and I was fit by all possible standards (rather than fat % 🙂 ). Gary’s book opened my eyes and changed my life. I find your blog now incredibly helpful as well, esp. with your take at combining low-carbs with sports. Thanks for that!

    Now to my question: even though I adopted low-carb / paleo diet some 2 years ago, I’ve been on a strict keto-diet only for some 3 months now. My main source of fat is coconut oil. I supplement it with meat. It works great, I feel great, running or cycling long is not a problem, doing sprints or hill runs is not a problem. Hard climbing is. My main game now is bouldering and it requires greater power output which is, so it seems, glycogen dependant. What would be your recommendation in that regard? Would increased does of L-Glutamin help? I’ve read Lyle McDonald’s book on ketogenic diet and started experimenting with Cycled KD, i.e. I eat some starches (mostly sweet potatos and vegies) on the weekend but then I always struggle a bit with going very-low-carb again in the week. Any suggestions how to make ketogenic diet work for power sports?

    • Martin

      OK, I’ve reread your post. Lesson 2 seems to be what I’m interested in. So what would be your final position on supplementing BCAA prior to a HIT workout (in my case, a bouldering session)? And would L-Glutamine be helpful as well?

      • I use BCAA during and Glutamine after, but I’m not sure there is a “right” way to do it.

    • Try UCAN super starch.

  • Lal Beral

    Regarding the ice cream addiction potential… there really is something about cream in general that is unique. I could easily pour myself an 8-oz. glass of heavy cream, drink it down, and have another. That’s like 1600 calories. Try doing that with butter, or coconut oil. Ick. Cream is special, and for that reason I need to stay away! 🙂

    Cream plus coffee is even better!

  • John M

    You say:
    >Because muscle can’t export glucose (muscle lacks the enzyme glucose-1-phosphatase), <

    But, 1) then how do they access the glycogen at all, since it is my understanding that g-1-phosphatase is how the polymer is hydrolyzed; and 2) "can't export" should be due rather to some kind of membrane transporter (like Glut maybe or is that only for import…?) shouldn't it?

    • Muscle can IMPORT glucose via GLUT-4, but once it makes glycogen of it, it cannot export it, because it can’t make glucose again. Glycogen is broken down into glucose-1-P, which cannot leave the cell. Glucose-1-phosphatase (present in the liver), take the P off G-1-P so glucose can be exported.

    • Martin

      Hi. I want to ask to Peter. In you article Ketosis – advantaged or misunderstood state? (Part I), you have wrote the enzyme is glucose-6-phosphatase, no glucose-1-phosphatase. What is right? thanks

      • G6Pase is present in (normal) liver, but not muscle.

  • Susan

    CALL ME CRAZY– but I’ve been on a search for your wife’s low carb ice cream recipe and although I see you reference to look for it in previous response, I can’t find it! Can you please make this easier. I love all of your posts– keep it up.

    • It’s a comment I posted March 7 under part I of this post.

  • Joe Smith

    I couldn’t find the ice cream recipe by using your search field. Apparently, the search feature doesn’t peruse the “comments”, only the articles. Is this a behavior you choose, or is it hard-wired into the blog’s software?

    I did eventually find the recipe, so no need to provide a map to it yet once again, but I thought I might bring to your attention that, if you have a choice, there might be something to be said for letting the search feature look through the comments as well as the articles, particularly in a blog like yours where this is so much additional and relevant information posted in the comments.

    • This is a harder problem to solve than I imagined. Every time I find a plug-in that can search comments it has 10 horrible features that render the rest of the search features utterly useless.

      BUT — don’t be afraid to bust out the old CTRL-F trick. I was zipping around the comments using this today.

    • Lacie

      The best way to search comments is use Google and do a site search that includes the term you’re looking for: ice cream recipe

    • KevinF

      Face it, you’re gonna have to add the recipe to the FAQ…

    • Joe Smith

      Peter: I did try to use Control-F, but it didn’t work because the ice cream recipe was hidden from, and therefore unavailable to, the browser’s “Find” capability by being back a page or two in the three pages of comments.

      Lacie: I tried your idea but it didn’t work. The Google search you suggested did indeed take me to some discussion of those three words, but it wasn’t so easy to find the recipe and I’m not even sure the recipe itself was among the results that Google gave. To eliminate confounding variables, I Googled one of the more unique words from the recipe: espresso

      …and Google couldn’t find the recipe. Try it for yourself. Thanks for the idea. If I could get the idea actually working robustly it wouldn’t be a bad fix to the problem.

      • CTRL-F is working for me, provided you’re on the right page (remember, there are 3 pages of comments).

  • lorraine

    Thanks for this series on ketosis and training. There is a lot to ponder and assimilate, and as someone who just discovered you, I’ll be sifting through these posts a few more times I’m sure. On first hit, though, a couple of questions:

    When I first read the change in RQ that you experienced, I thought that the change was in the range for training effect alone and that I wouldn’t account for it from ketosis. Then it occurred to me that you were probably trained previous to starting a ketogenic diet. I quickly looked through your history and also saw the max test, but I’m still not quite certain of the whole timeline thing and whether or not you were trained to the level of this current post previous to the onset of ketosis. I’m trying to ferret out the training effect from the ketosis effect. It seems that you were trained but that first VO2 peak isn’t consistent then. Could you clarify this for me?

    I ask because the metabolic advantage thing is, of course, the thing.
    And also because when you look at the above substrate graphs of the three workouts, and you consider ketones a proxy for ffa’s, then the graphs look pretty regular vs. intensity. So again, I’m trying to ferret out the possible advantage or “improved metabolic flexibility” as you call it, of ketosis over a mixed diet.

    Just a comment on fuel utilization as you mention you’re going to write a post about it later. And please forgive me if I’m misunderstanding what you’re saying and I’m about to be an arse and tell you something you already know, but it caught me when you said, “Whenever our bodies can’t access sufficient cellular oxygen, our metabolism shifts”…. There’s never a time, irrespective of exercise intensity, that we’re unable to access oxidative metabolism. Even at VO2max there’s sufficient oxygen pressure in the mitochondria to effect oxidative phosphorylation. Non-oxidative or RAPID glycolysis (anaerobic) is simply additive. As intensity increases, along with an increased recruitment of FT glycolytic fibers, oxidative routes just can’t keep up with the rate of muscle demand for ATP, so the short glycolytic pathway is increasingly added as a supplement, not as a replacement, to oxidative routes. While cranking out a relatively puny amount of ATP per glucose, it nonetheless does it fast; ergo, the name rapid glycolysis. So this is why a true VO2max achieves an R greater than (the symbols don’t seem to be working in the editor); 1 – you have all the CO2 from oxidation PLUS the CO2 from the buffering of lactic acid from rapid glycolysis. A true VO2max reflects the oxidative pathways cranking at full tilt along with the supplemental glycolytic pathway adding it’s supplement. If this is how you understood it to be, please forgive the lecture, I misunderstood you, but your statement about the “shift” and inability to access oxidative metabolism made me think you were describing the moving out of one pathway into the other, instead of the addition of one pathway onto the other. As an aside to this though, I was also wondering about your decrease in VO2max on your second GXT, and thinking that maybe they didn’t take you all the way to R greter than;1 before calling it a max.

    • Lorraine, great questions. Let me clarify:

      1. Fitness/training were effectively the same between the tests so, yes, the RQ changes were virtually all due to the nutritional shift. Keep in mind, I’m not the first to write or talk about this. Bob Seebohar has written about this, and Steve Phinney has on several occasions going back to 1982. When you remove carbs from the diet (even shy of ketosis), the body increases its ability to access fat stores.

      2. Yes, I understand your last point, and so I’m oversimplifying a bit technically. The practical implication, however, is still that at RQ >= 1, the amount of substrate going through the mitochondria is very small, which implies fatty acid is not much of a substrate at all, hence the “glycogen dependence” idea.

      3. As for the difference in VO2 max (both in absolute VO2 volume and on per kg) — great question??? I definitely felt (and still feel) like I have a bit less glycolytic power, but I was still surprise when the test stopped. I guess it’s possible we should have not further, but it’s not clear I had much left.

  • Dave

    Can you elaborate a little on what you mean by, “But keep in mind, my muscles CANNOT export one gram of the glucose they store, so any glucose in my bloodstream is either ingested (which I didn’t do) or coming from my liver, which CAN export glucose.”?

    I don’t really understand the difference between using muscle glycogen vs. liver glycogen. Is the reason that you need energy from HGO because your muscle glycogen stores are depleted? When you say they can’t export glucose, does that mean they can only fuel their own muscles but not redistribute fuel to other muscles/cells that need it?

    • See previous response to this post on March 15. Yes, that is the implication — muscle glycogen can ONLY be used to supply glucose the muscle.

  • lorraine

    Thanks, Peter. On the RQ again, did you control for weight change like Phinney? I’m only trying to get at the real impact of ketosis vs some other confounder because your results are so dramatic. Phinney’s studies were small, but likewise impressive, so any additional n’s are useful. Haven’t read Seebohar, but will.

    Yeah that glycolyitic peak power thing is a little puzzling, if only because something that improves performance even thru HIT with such effective glycogen sparing, fails when approaching max.

    Thanks again.

    • The weight difference was trivial, plus in only impacts the per kg numbers. Same for training difference. I would guess virtually all of the difference was due to eliminating carbs and reducing insulin levels to unmeasurable amounts (literally). Phinney’s study used a cross-over, so even though it was small, it’s quite powerful.

  • N=1 with a glucometer yielded some serious swings in glucose for me while pricking myself in the finger intermittently during a HIIT session of 1-minute intervals of 100%+ VO2 effort followed by 3 minutes of recovery in between.

    Would be interesting to get a streaming reading of some of these numbers rather than just pre-and-post.

    I know Tim Ferriss wrote about — actually I can probably find it with a search — here it is:

    DexCom Seven Plus ( The DexCom Seven Plus is the continuous glucose monitor I used and abused. It is an implant that gives you the approximate data of 288 fingertip blood samples per day.

    It would be great if the technology could yield some good devices that could track real-time biomarkers such as insulin, lipids, etc. so you could track your workouts — and everything else — that would probably help elucidate some of this stuff further.

    • It sure would. Insulin is hard nut to crack for point of care, though, for reasons I could bore everyone to tears with.

  • Mark

    Since you mentioned the super starch, I decided to give it a try. I do a lot of heavy lifting and thought the extra carbs might help. So I have been drinking the 30g packet of super starch about a half hour before working out. My energy is up for the heavy lifting endurance work outs and I’m not feeling week on the big lifts. Push pressed 205lb today and it felt good. Although, we were doing heavy snatching yesterday, after snatching at the heaviest weight, I felt like passing out. I had to stand still and bend over to pull myself together. This has happened to me a few times when going very heavy on the ketotic diet. Just thought I would give the info to anyone interested.

    • Are you supplementing with an additional ~2 gm of sodium per day (i.e., at least 4 gm of total sodium per day)?

  • Mark

    I am taking at least 2 grams of salt per day via bullion. I’m not actively paying attention to salt intake beyond the 2g from bullion. I’m also taking 350mg potassium per day. I work out at 6am. My breakfast consists of 30g super starch per-workout, protein drink directly after workout and a cup of water and bullion about an hour after that. Sometimes I’ll have a heavy cream latte before the bullion. It is great that this blog has information about interplay of ketosis and working out. Thanks.

    • Try increasing the salt a bit and adding some magnesium.

  • Mark

    Sorry, I take 350g magnesium and no potassium.

  • Mark

    I mean 350mg of magnesium.

  • John P

    Peter, Before you totally eliminated carbohydrate from your diet,In time did you notice or feel as if you body was becoming more efficient at switching fuel source to stored adipose? I’ve gone no carb off and on for almost 3 months now with a weekly cheat of a quality beer and couple pieces of pizza or whatever I fancy. I have no proof but it feels as if my body is becoming more efficient to partioning fat for fuel. what do ya got? Thanks!

    • Absolutely. You do not need to be in ketosis to experience the benefits I’ve described. They will likely be less pronounced in most people, than in ketosis, but they are still absolutely present. The lower your average circulating insulin levels, the better your body is at mobilizing (rather than storing) fat.

  • lorraine

    Thanks again, Peter, for replying to my RQ questions. Now that I’ve had time to look around here more thoroughly (it takes awhile, there’s an amazing amount of information from your self-experiment!), I see that all of my questions were answered “in there”.

    I also watched your presentation on JumpstartMD, and right now my number 1 project is to find out how the constant in the HOMA-IR equation is derived, because the rest of that equation uses fasting glucose and insulin, and yours were just fine, but that post-prandial insulin was killer (literally). A colleague and I were just laughing about how “evolved” a diabetes doc is that he reports to because at least he’s regularly ordering fasting insulin….sigh.

    Thanks, too, for your hard work (and personal sacrifice I’m sure) for joining the roadshow that’s trying to change clinical medicine. The early pioneers like Atkins and the Eades, and even Barry Sears, had to take the heat alone. I really believe that with you joining Taubes, and Volek and Phinney and Westerman and the Eades and Lustig, the influence of the technically articulate may soon reach critical mass.

  • Dr. Attia, can you give me some idea of how you determine when you use UCAN and how much, with regard to cycling?

    • Highly variable and dependent on nutritional state. You’ll need to figure out what works for you. Start at, say, 25-35 gm/hour (much more than I use).

    • No surprise there… I’ve been <50g CHO for a little over a week… I have done up to 4hrs (Zone 2) without any supplementation. I read that Dr.Phinney does 3hr rides at 18-20mph without supplementing, but I didn't know if it was an intensity based thing. I live in the mountains and it's hard to do a ride and not get considerable Zone 4. Just trying not to shoot myself in the foot…

    • Dr. Attia, I apologize, I’ve botched this badly… What I was trying to ask is if there is a way that you know that you _need_ to supplement with UCAN? I know what it feels like to bonk… and I know what it feels like when I need to eat something when I’m not doing low carb… Is there a corresponding ‘feeling’ when in ketosis? I’ve not had any similar sensations despite riding what would have been long enough to induce them previously…

      • I don’t know how to answer this question? Need is a strong work. Certainly one doesn’t NEED much. It all depends on what you’re optimizing for and what your biologic characteristics are.

    • I’m sorry, I’m probably not being very clear… When you (Dr. Peter Attia) did the ride in this article, why did you supplement with UCAN? After you determined that you would need/want to supplement with UCAN, how did you decide on 50g?

      • Partly to conduct the experiment, party to augment some glycogen. I certainly didn’t “need” to to complete the ride.

    • Thank you, and thank you for your patience…

  • Lacie

    I just got back from a backcountry canoeing weekend, my first since going very low carb. I think I have some tweaking to do on this diet when it comes to my sport. Something about the upper body workout that paddling gives me makes my digestive process immediately cease – not good considering that most low carb food is heavy and slow to digest. Just a guess, but I think swimming could be similar. I haven’t experienced this type of stomach upset with sports that rely mostly on my legs, such as cycling.

    I’m wondering about doing a liquid diet during the day and saving solid food for in camp at night. I don’t need to be in ketosis, but I like to stay around 30g of carb per day. Maybe a combo of UCAN, whey protein, and MCT oil. It’s hard to imagine paddling for 7-8 hours a day on this, but I’m willing to experiment.

    On my trip over the weekend I ate grilled steak and chicken packed in ice, a lot of nuts and nut butter, cheese, and a few dried dates. Aside from the stomach upset, I was very happy with how the diet fueled my body – no flameouts, no carb cravings, and I only had to eat every 3-4 hours, instead of every 1-2 like I used to do when I fueled myself on carbs.

    • Great work. Keep tweaking away. I find that sodium by itself is not enough for me. Needs to be in liquid form, which is why I like the bouillon so much.

  • Maryann

    Hi Doctor, I looked through the Volek/Phinney book as you suggested, and I don’t see what type of potassium to use. Vitaminshoppe has citrate, chelate, gluconate, aspartate, chloride… I don’t know what to get or what a minimum, safe dose is for a petite person. Thank you for your help, maryann

    • Not exactly clear (to me, at least) which is best. I’d probably start with citrate, though. Of the “big 3” — sodium, magnesium, and potassium — that’s the order of importance, so if you get the first 2 right, you don’t need much (if any) supplemental potassium.

  • Scott

    Do you have more details as to what exactly our bodies do with UCAN? Is the idea that it just digests so slowly that the insulin response at any given time is negligible? Or does it follow some different metabolic pathway ala fructose? I guess I’m just trying understand a carb that doesn’t affect blood sugar or insulin, as that seems somewhat contradictory.

    • Ultimately, exactly what we do with glucose, but just in a very SLLLOOOOOWWWW fashion. Think of super starch as a time-released glucose.

    • Maryann

      That is a great help; I will hold off. Thank you very much! maryann

  • Mark Bennetts

    I have taken up rock climbing since January, and noticed the following, after a few days of climbing in a row:
    When I come down to the ground and rest in between climbs, there is a feeling that there is fire in my forearm muscles, my upper biceps and sometimes elbow joint (but not the actual joint it feels like the muscle around the joint) and pulsates as my blood pumps…
    This will linger for a good 3 – 4 hours, and only stops happening when I take 4 – 5 days off
    When I’m on the wall climbing it goes away and I dont feel any of the pain.
    Lately I have noticed that I have been climbing less days in a row now before this begins occurring.

    Im 6′ 2″, 177lbs, ~17.5% body fat, I eat less that 50g carbs a day, and am trying to reduce my protein intake, I’m down to about 140g, while filling the rest in with fat. I eat a good cup of sautee spinach with salt and half an avocado everyday. and using my fat reserves to climb lets me go for 2 – 3 hours sessions, with probably half of that sitting down resting, just have to make sure my heart rate doesn’t sky rocket doing new moves on the wall!

    Do you have any idea what is causing this?
    Am I simply having too much omega 6?
    Does omega 3 counter balance omega 6 issues, or is omega 3 just a better substitute, ie 50 omega 6 is okay if I have 50 omega 3 to balance it?
    Is there a nutrient that I am low on?

    Lots of questions, thanks for all the great work you and Gary have done, and I hope you get a chance to answer some.

  • Dave C

    I have a question about sodium which I guess is tangentially related to this topic.

    I have been in ketosis for about two weeks now. I rarely go over 1700mg of sodium a day. My recent (3/9) metabolic panel showed my sodium at 141 mmol/L and potassium at 4.8 mmol/L … I work out about 6 days a week but do not push myself into Zone 4+ as much as I’m in Zone 3.

    Are these numbers from the panel even relevant to your point about sodium? Given that I’m still borderline hypertensive I’m very wary of 4,000mg of sodium per day not knowing how much I’m passing in my urine.

    • If you’re not symptomatic at all (light-headed, cramping, etc.), hold off. I suspect at some point you may need it. I’ll still suggest 400 mg/day of Mg.

  • Debra

    This is a little off topic, but about the ice cream (sorry-but you did mention it in the post). Xylitol is converted to glucose in rats (I assume in humans too?). I don’t know if the conversion to glucose is complete or partial and I don’t know how much is absorbed in our gut.It also has some inhibitory effect on ketogenesis in rats. Now your ice cream doesn’t have much xylitol in it but it must have an effect on someone trying to be in ketosis much of the time?

    • Xylitol’s inhibition of ketosis is probably subject dependent. Steve Phinney, for example, has some unpublished data (I think “n” was small, maybe 25, but I don’t recall), showing no inhibition, but I do believe (especially in large amounts) it might inhibit B-OHB formation. In some people more than others, of course.

  • Dr. Jeff Volek does a good job breaking down the benefits of UCan Super Starch in layman’s terms in this video:

    Dr. Attia…I imagine this is a product you would use when you need to be at your peak performance, but not necessarily for everyday training?

    • Do you mean me personally or “one” in general?

    • You, personally. You mentioned you’d take on UCan’s benefits in a later blog, so I was just interested in how you currently consume the product. Thanks.

      • Super-intense activity where I want a little more glycolytic power. So I will use for any workout (swim, bike, lift), where the intensity is expected to be sufficiently above threshold for long periods of time.

  • Garry

    re: MCT and ketones

    I’ve seen the use MCTs promoted for Alzheimer’s patients because MCTs produce ketones. There’s a prescription “medical food” called Axona which is a caprylic acid-based product which purports to do the same thing. Can MCTs or Axona or coconut oil appreciably raise ketones without the patient also restricting carbs? That just sounds too good to be true: all the benefits of a ketogenic diet without the diet.

    • Not quite so simple. Consuming MCT oil does generate ketones, but it’s quite transient in the presence of a “normal” diet. I think the best of both is MCT plus a ketotic diet, especially if your goal is ward off diseases like cancer and Alzheimer’s disease.

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  • UltraVoltron

    I just have a quick question as to the effects of adhering to a low carb diet, IE 50g a day and carb loading the day of competition? Would that eliminate the metobolic benifits of the diet? Would it make all the low carb dieting during training worthless on your LDL, HDL and Triglycerides?

    • Two separate issues, here, I think. In terms of overall health, I think one day per week of adding back carbs probably has a small effect. However, what it “gives” you in glycolytic power, it might “take” from you in oxidative flexibility.

  • Kathy

    Hi Peter, Thanks for all your great work.
    I had an interesting experience this past weekend regarding ketosis and exercise. I have been in ketosis for nine weeks now. I am moderately active (probably very active if compared to mainstream America – lots of fast-paced hill-walking and farm work) and relatively fit. 53 years old. On Sunday we cut firewood for the first time in 5 months. I ran the chainsaw for over two hours, putting it down only to refill the gas (once) or to thrown (mostly large)logs out of the way. Normally, doing this kind of intensive, heavy labor with no build-up would have laid me flat that afternoon. Instead, I felt like I had done nothing much at all, and still feel that way today. I find this remarkable. It makes me think that the low-carb diet has made a major difference in my joints – no stiffness! In addition to having made it so I just worked, steadily, and only quit when I did because I was worried about the consequences, given the lack of working-up to cutting wood slowly. I wasn’t ravenous for lunch, either. On carbs, I would have been shaky and desperate for food.

    • Kathy, this is great to hear!

    • Kathy,

      I experience the same thing now. I used to really struggle with exercising, not doing work out type of exercising, but really anything physical, ie playing with the kids, working around the house. I would be wasted by the early evening and wake up with sore joints. I am only 40, so didn’t really think that this was normal. Now I work out every morning for an hour, I am still able to stay up late and get up early, I don’t have joint pain nor sore muscles. (but the lack of sore muscles probably means I am not working out hard enough)

      This is ALL down to high fat, low carb. The fact that I am also losing weight makes it such a powerful path for me. There is no turning back for me. I have been doing low carb for 18 months, but high fat, low carb for a little over eight weeks.

  • Kathy

    Thanks, Peter and Travis for your responses.
    Travis – I agree, no turning back. I can’t believe how much better I feel. I’ve lost 15 lbs and would like to lose another 10. Most people would have said I was “fine” before – I’m 5’9″ and weighed 167, with a fair bit of muscle – but I think when people said I looked “fine” they mean relative to how everyone else looks! I love losing the weight but I love even more how I feel and then when I think of what this means for my long-term health – there is definitely no turning back. I’m not sure if I’ll ever eat more than 20gms of carbs a day. I don’t miss them, which I find amazing. And, there are now FIVE people in my office following low-carb diets as a result of my talking about it and providing articles by Gary Taubes! This is a REALLY big deal, since I work in public health.

  • As a 260lb T2 Diabetic, I use a <30g a day ketogenic diet to successfully control my BG levels. Most of the time my BG remains below 100mg/dl, however I run 5k races every Saturday morning at about 93% max effort and find that my post-race BG can hit 180mg/dl or more, despite not injesting any food before the race.

    Most references seem to suggest that the liver's glycogen supplies have to be exhausted before ketogenesis can commence, so I've been surprised that I can have such a spectacular liver dump while in ketosis.

    Lesson 2 is therefore a great relief to me (although I'm less than thrilled at getting a huge BG spike because of exercise).

    The great news is, that after 2 initial terrible weeks, I've managed to knock over 2 minutes off my 5k PB since going on a ketogenic diet!

  • Susan G

    Hi Peter,
    I’ve read from many sources that while it takes the body some time to transition to ketosis, one bite of sugar or starch will throw you back into glycolysis. Is this true? If so, why would the body be so ready to abandon ketosis, especially because it is healthier?

    • It’s a great question! I have had “bad” meals that knock me out of ketosis for anywhere up to 2 days (that happened once). As we didn’t evolve in a food environment that looked anything like today, it might just be that we didn’t need to have this ability?

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  • Jessica

    Hi Peter. I wrote to you a few weeks ago about the use of superstarch for long distance running. I didn’t have time to get my hands on some and try it out prior to my last race and so just went without. But am happy to report running the Boston Marathon in 4:01 on VLC diet. Pre-race dinner was roast chicken and dark meat, spinach salad with eggs, bacon, avocado. Breakfast of 3 eggs plus extra yolk cooked in butter 5 hours pre-race with an avocado 2 hours pre-race. Tried to “salt-load” in anticipation of heat/dehydration factor. Honestly, I felt horrible throughout the race but so did almost everyone else (who had not been training in a warm climate).. We we waiting around for the race to start in the sun in Athlete’s Village for 90 minutes before the start and I felt dehydrated by mile 3. If you didn’t hear, temperature soared to near 90 by the finish. Wanted to prove I could run a decent race on VLC and I’m pretty satisfied. Time last year at Boston was 3:37 in ideal weather on more typical diet and using carb supplements (GU, Gatorade, etc) Q45 minutes thru the race. My weight is the same. Have been doing more intense strength training this year. Started training for Boston later this year so less sessions of speed work. Hard to know if diet, weather, or training differences (or combo) slowed me down. But in any case, will take slightly slower time in exchange for feeling great, satisfied and less food-obsessed since lowering my carb intake. Off to run the Big Sur Marathon this weekend. Although still recovering and on a very different course, will be interesting to see how my time compares without the heat-wave factor. As a physician with an MPH, I love reading your blogs. Your are doing a fantastic job of teaching readers how to look at the medical liit with educated skepticism. Thanks for all of you effort! Signed, another n of 1

    • Jessica, hard to make a comparison, I’m sure. Conditions in Boston were pretty tough this year if the lead runner’s times were any indication.

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  • Karin

    Hello Dr Attia! I have been on a ketogenic diet for approx. 6 weeks now. I went on it to see if it would help my migraines (which are exceptionally chronic, often silent, and sometimes basilar-type) and it worked so well I was able to ditch the propranolol and verapimil. But so many on this diet seem to disregard exercise, which means finding information on exercise and low carb diets extremely difficult to find! Personally I do quite a bit of exercise, lots of swimming and lifting. I’m finding swimming to be easier than ever on this diet, but lifting is generally more difficult.

    I have a question. Do you think there is a correlation between people who tend to have good endurance abilities (vs sprinter types) and their ability to easily transition to a ketogenic diet? I didn’t get the infamous carb flu and my body generally seems to prefer this diet to the traditional low fat “healthy” diet I was on before. Also whenever I eat a bit too much carbs (or drink too much) and I transition back into ketosis the next morning, my body tends to get really shaky for an hour. Do you know what causes this?

    Thank you so much for this article! I find it fascinating no one talks about the glycerol part of triglycerides, it makes sense your body would make do with replenishing the glycogen stores by using fat instead of sugar. Maybe instead of people recommending carb loading we should be recommending eating more coconut oil instead.

    • Great question, Karin. I do not know the answer and have not seen any data suggesting this to be the case. One could make a teleological argument, though.

  • Annette Byrne

    Thanks so much for this terrific resource. I am a Lecturer in Physiology at an Irish medical school and full time research scientist so really appreciate the rigorous hypothesis driven approach you take . Its convincing, realistic and scientifically justifiable which it much appreciated!
    My question is related to my personal situation- In 10 weeks time I take on Ironman UK—Goal is to ‘ just finish’ and the race will likely take me 15h +. I have been ( like many it now seems) unable to drop body fat since starting IM journey in January, despite hours of good quality training & eating a mainly organic high quality diet. I completed a Half Ironman in training yesterday and there is no question I need to drop as many kgs as possible before race on July 22 ( in order to make hilly race bike leg and marathon tolerable). Some weeks ago,a local nutritionist suggested I go ketogenic which I have resisted ( as I do > 16h training per week) but your site has me convinced.
    My questions:
    1. With 10 weeks to go is it too risky ( re training performance) to go ketogenic ?—I will supplement electrolytes & keep protein down to minimize side effects
    2. If I take in high GI carbs on long bike rides only will this completely negate the efforts of going ketogenic for the rest of the week—I don’t think there is enough time for me to acclimitize to the keto approach to long sessions
    3. On keto diet is the concept of a ‘ cheat meal’ completely off limits ?
    Many, many thanks

    • 1. In my opinion, 10 weeks is probably feasible. It took me about 12 weeks to feel 100%++
      2. Yes, you should avoid high GI carbs, even on the bike, if you’re ketotic. Low GI carbs (e.g., cashews, Super Starch) are much preferred.
      3. Correct, no cheating in ketosis. It takes days to get right back in.

  • Xiaolei

    Hi Peter,

    Thank you for another excellent post! I did experience lose of explosive power during my basketball play but my endurance has improved dramatically and made me a second half monster. My weight lifting sessions have been less than ideal until I fixed other related variables you mentioned and my progress in weight room has been progressive and steady.

    However, I do have a question about eating. When I was on a high carb diet, my appetite is huge and I am constantly hungry. After switching to high fat diet (around 40g carb per day), My appetite became a non-issue and I rarely feel hungry. However, if I eat only when I am hungry, then I might eat only two meals a day. I currently eat every three to four hours even though I am not hungry. So my question is: if I eat the same amount of food everyday, does it make a physiological difference if I consume them in three meals or five meals? Or do you think scheduled feeding is a bad idea and it is best to eat whenever one is hungry? Really appreciate your time.



    • There is a lot of discussion about this, and I have not yet had the time to do my own research, so I can’t really comment on it with credibility. Hope to soon.

  • DavidM

    Hi I’ve seen around the place, esp. in the bodybuilding arena that a carb-up day is recommended if not essential to replenish glycogen stores in the body esp. if you are exercising.
    Do you recommend a carb-up day?
    There will be issues with trying to get back into ketosis which will take several days, but can your body make sufficient glycogen stores to replenish your muscles?
    your thoughts?

    • Probably depends on too many features to comment on quickly. Not really sure on the data.

  • Brian

    can’t wait for that future post on Generation UCAN

  • Keith

    You say that one is either in a state of ketosis or not – with no shades of grey. How does this affect the ratio of fat to glucose used during aerobic exercise? Is there a switch or a continuum? I like your ratios, where you conserve glycogen. Perhaps I’m asking whether you think fat utilisation increases on a low carb diet whether or not you happen to be in ketosis? The reason I ask is that I am on a low carb regimen and can manage 5 or 6 hour hilly bike rides ( albeit nothing like your pace) without bonking and (mainly) resisting the cake at coffee breaks, but don’tknow how close I am to the edge. Maybe it doesn’t matter, but I’m curious. Also I suspect I may eat more protein than required to be in ketosis. Any thoughts?
    Thanks. Keep up the good work.

    • No, the gradation between aerobic and anaerobic is a continuum, not binary.

  • Keith

    Thanks I understand that but I was really asking about the fat to glucose ratio of fuel during moderate aerobic exercise and the effect of ketosis on that. I’ve seen your data and wondered how critical ketosis is to the high fat usage compared with just a low carb diet but not quite in Ketosis.
    Sorry for being unclear before. Thanks

    • RQ, which is the ratio of VCO2 to VO2, is a continuous variable, so again the ratio of fat to glucose oxidation (and glycolysis to fat oxidation) is continuous, not discrete. What ketosis does it “shift” the RQ curve. I hope this helps.

  • Brian

    Hi Peter,
    don’t know if this is the rigth place to post this question.

    Can there be a correlation between knee pain (in the joint) and a very low carb diet ?
    Since going very low carb I have experienced pain in my knees during my long training runs (>15 miles) and was just wondering if I migth need some special supplement when training for ultra runs and going LowCarb ?

    As for now I’m not taking anything apart from ekstra salt and occasionally bouillion.

    Apart from this little problem, I’ve only experienced positive changes during the 2 months below 40g of Carbs / day – I feel very good in training, especially during runs that exceeds 2 hours.

    Great blog and can’t wait for the Nusi to start

  • Melanie

    Love the blog Peter!

    I am someone who is out to win an Olympic medal, in a sport (biathlon) where my races are typically 20-35 minutes long so I mostly race just above anaerobic threshold, with sprints needed for surges during the race and at the finish. I see the benefits in keto-adaptation but I also see possible drawbacks in my performance and I am trying to find a balance between the two by consuming a low carbohydrate diet (but not below 50g/day) and low-glycemic diet. However will this just put me in the state where I’m not fully keto-adapted but not consuming enough carbohydrates to fuel my body, i.e. nutritional hell?

    • My guess would be that full-blown ketosis is not idea for your race. Rather, you’re probably better in a sugar-reduced, but non-ketotic state, primarily for the sake of training.

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  • markus

    CrossFitter, although right now I’m in a season of OLY lifting and lots of strength/percentage training at lower volumes/higher loads. I eat a mostly keto diet with the exception of lifting meets and high intenisty metcons where I consume a little pre-workout (medium chain triglycerides, fructose, and electrolytes) about 12g sugar pre workout during weight lifting sessions and metcons or days of multiple workouts…also replenish glycogen with coconut water/sweet potatos…would you save the pre just for the higher intensity wods? Wanting to compete in the future at the games! Mostly hitting high fat, moderate protein otherwise, with a little IF until post 10:30am training sessions which go until noon! Cheers

  • Hi Dr Attia

    Thank you for the amazing information, I am learning so much.
    I am a chiropractor practicing in Stockholm Sweden. I am doing my 2nd masters degree. I am doing it at the Swedish school of Sports and Health Science and am about to decide on a study for my masters thesis.
    After reading your info I am really inspired and intrested in the adaptation from carbs to fat/ketone based fuel sources – what you decribed in “How a low carb diet affected my athletic performance (Part 4)”. Also based on my own experience.
    There seems to be alot of conventional wisdom to break through when I talk to people at the university about this concept.

    I know you must be very busy but wondered if you have any advice on the following 2 areas.
    1. As a study, would it be worth doing a comparason study of one or a few cyclists going from carb to fat as fuel source. Or would it be better comparing fat adapted with carb based cyclists? I thought of measuring the parameters you used in “How a low carb diet affected my athletic performance (Part 4)” Do you have any other suggestions for a study.

    2. I need to try to “sell” the concept to a tutor, as I said: break through some conventional wisdome. Any sources of literature you can recommend. I understand that Jeff Volek and Steve Phinney should be read, anything else?

    Kind regards

    • Steve Phinney did a great study while at MIT in the early 80’s where a group of highly trained cyclists, in a crossover design, did standard diet vs. ketogenic diet. Take a look at that. Repeating this study with recreational (vs. highly competitive) cyclists would be very interesting. With a crossover design you could adequately power this study with far fewer subjects. As far as other sources, looking at the references in their book is a great place to go.

  • Daniel


    Awesome blog.

    I am in week 2 of keto adaptation after being inspired by the Volek and Phinney book. I am still wondering how much of an advantage (if any) keto adaptation is for endurance exercise. You calculated (in “Lesson 4”) that you would last 5h instead of 2h15min on carbs. But in Phinney’s 1983 paper that studied the 5 cyclists, their time to exhaustion did not actually increase significantly, despite a much lower RQ. In addition, they didn’t consume carbs in the pre-keto test, as they would have in a race, so keto comes out looking like a pretty poor choice there (I realize there are other advantages, and I care about those too!).

    I am also surprised that they (and you!) used such a low intensity level, 65% of VO2max. Is *any* kind of race done at this level of intensity? It would be really interesting to see RQ numbers in, say 5% increments for a keto-adapted person vs a non-keto-adapted person. At what intensity or at what race distance do you think keto adaptation provides a benefit, for us mere mortals (as opposed to elite athletes)?

    • Ketosis may not provide any benefit for a 400 IM (5 minute all out), but the point about RQ is for events lasting over ~3 hours. The longer the event, the more benefit to keto-adaptation.

  • David Ma

    I was curious as to why you only last 5hrs whilst exercising.
    If you body still had stores of fat, do they convert to ketones as you exercise, replacing what you had lost?
    So then is it possible to keep going until you’ve exhausted all the fat stores in your body?

    • This point is only looking at stored glycogen capacity, not the aerobic utilization of fat, which, as you suggest is nearly infinite. This is a complex topic and worthy of its own series (or book, actually). I’ll address this in the coming year.

  • Bruce Caward

    I’m heading up to the Sierras for a week-long off-trail high-altitude carry-everything-in-and-out hike, in a week. It’s around 80 miles, mostly up between 11- 13,000 feet, with lots of up and down. (i’m 55, 190 lbs, fit.)

    Last year I took the normal stuff (Clif bars, etc.) and did fine. But I’ve been experimenting with your high-fat diet for the past few months; I feel great, and am fascinated with trying it out in a remote, sort of survivalist adventure. Is this a really dumb idea? (Once I get up there, there’s no turning back for the week.) I love your whole basic idea about not “hitting the wall” through burning fat, and thought that up there I could rely on my stored body fat as a fuel I don’t have to carry in my pack.

    Can you recommend some portable nutrients to take? So far I have:
    Coconut oil
    MTC oil
    boullion cubes
    mag/potass suppliments
    fish oil
    tuna or salmon packets
    chicken packets
    nuts (?)
    Jerky (?)

    Can you suggest anything else? Whey protein? Super starch?

    All the backpacking nutrition sites I found online, and there are many, take the carbs=good/fat=bad line. But I love your story, your research, and my experience with it. So I’m looking to you.

    Bruce Caward

    • I think you’re on the right track, Bruce. SS is highly recommended.

  • Daniel

    Do you use sodium or other electrolyte supplements *during* prolonged exercise, particularly in the heat? Or do you feel that it is enough to add the extra sodium as bouillon etc at other times during the day?

    • Only REALLY long stuff. Anything up to about 6 hours and I’m fine with just water +/- some super starch or nuts (both of which do contain sodium).

  • Dwayne L.

    What do you make of this high fat / increased serum LPS connection? See:

    • You’ve got to very careful drawing conclusions from any study that feeds fat to mice. Mice are herbivores, so their metabolism of fat is very different from ours. Just because cats are harmful to mice, doesn’t mean they’re harmful to humans.

    • Dwayne L.

      Thanks! I wonder how expensive a serum LPS test would be, say along with a C-reactive protein screen if one were interested in a base line at the beginning of going paleo and then again in six months to a year? I was just thinking about the “leaky intestine” hypothesis that Cordain mentions a lot in his book. With the vast amount of microflora in the the gut, one might expect a basal level of LPS getting through.

      Or as you say, just another example of a fine mouse study with little relevance to humans.

  • Hi Peter. I’m doing boxing and I have been in ketosis for a few months. What is your opinion on boxing in ketosis? Also, I’m currently doing the super slow workout once a week for conditioning and the rest of the days, I practice sparring. What is your opinion on my training methods?

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  • SusanneL

    Hi Peter!

    Im doing a lot of exercise and I have found out that I can still be in the optimum ketosis range while consuming both creatin and BCAA intake during my heavy weightlfting. When finished with my weightlifting-workout I tend to wait for some hour before I eat, not to go to hight with the protein intake under too short of timespan. The days Im doing more of a endurance exercise, I don´t take BCAA nor Creatine. I also do IF and “cykle” my intake of carbs (mostly round 5-15 g/day) and protein (higher but not too high on weightlifting days). I daily eat MCT-oil and coconutoil. It would be interesting testing the Superstarch UCAN when i do my weightlifting but as far I can see, it´s not for sale in Sweden. My question is if you have any opinion on intake of acetyl-L-carnitine, training in a ketonic state? Is there any benefit or disadvantage whit this supplement?

    • They can probably ship to Sweden. I don’t have a strong opinion on carnitine supplementation.

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  • Tristan

    I know Peter gets inundated with questions from half the would-be keto-questers in the world, so if *anyone* has any information to share with me, I’d really appreciate it. I’m going through a bit of a cancer scare; to be honest, really freaking out, and trying to get into keto and lower my blood glucose levels as rapidly as possible. I’ve been emulating Peter’s diet as closely as I can – almost zero carbs, moderate protein, and always the cleanest foods possible. I’ve been supplementing with generous helpings of omega-3 rich oils as well.

    Problem is, after more than a week of this, I just seem to be losing muscle mass, power, and energy, and my glucose levels, if anything, are *higher* on average than they were prior to my zero carb diet. I’m pretty lean and athletic already, so this kind of weight loss is not really desirable. I’m afraid my body is cannibalizing itself to maintain constant glucose levels, and if that’s the case, how is one supposed to deny blood sugar to hungry tumors?

    I know it’s a little off-topic, but if *anyone* has any advice of any kind, I’d really appreciate it. I’m kinda’ terrified, and desperate for quality information. Thanks to anyone looking!

    ps – …y’know, I think a forum would be really nice on this site. Seems as though a lot of people that visit would like the chance to talk with one another. I’ll bet it would attract a really nice, quality community, no?

    • Tristan, sorry to hear about the scare you’re enduring right now. Yes, I agree, a forum would be a good idea, and I’m trying to figure out a way to do it, where it will be maximally helpful and minimally annoying (e.g., rude, disruptive, destructive). If you’re feeling this way you’re likely off on one or two fronts: 1) too much protein, and/or 2) not enough sodium. Others can chime in with details and if you go through comments in other posts (e.g., What I eat), you’ll get all the guidance you need.

    • PaleoRocks

      Hi Tristan,

      The thing that really got me keto-adapted was fasted exercise in the morning before breakfast. I think most people are using ketones to some extent when they wake up since it is some time since the last meal. Try taking some coconut oil, some other fat or MCT when you get up, have a strong coffee and then exercise. Maybe this will help convince your body to use ketones more.


    • Raymund Edwards

      Thomas Seyfried — As a whole protocol to treat cancer as a Metabolic Disease using Calorie restricted Ketogenic Diet and two drugs to further restrict fermentable fuels to the cancer cells. Which are Glucose and Glutamine .

      “Pauline Davies: So what does it actually mean for a patient? How much do they have to restrict their diet?

      Thomas Seyfried: Well this is an important point and this is one of the reasons it’s a stumbling block. Some patients have to realize they have to stop eating for several days, and get their blood sugar down to 55 to 65 milligrams per deciliter and their ketones up to about 3 to 7 millimolar and then they know they’re in the state.

      So we have clear biomarkers for patients to get into this particular metabolic state. The problem is a lot of patients are reluctant, they have other thoughts, the issue of cachexia always comes up and they say, “How could you have a patient who’s losing weight stop eating?” And as I said, they’re losing weight because the tumor cells are mobilizing glucose from their tissues of fats and protein. ”

      “But you know if I had cancer, if I had a glioblastoma, I would stop eating for at least fourteen days and then I would take the drug protocol that we advocate because I know this would be my only chance of survival.”

      “Pauline Davies: Have you ever tried this yourself?

      Thomas Seyfried: Yeah people ask me that and the answer is I’ve tried it. How far can I go? Maybe two days, I’m still working. My students have gone a lot longer than I have. But you know if I had cancer, if I had a glioblastoma, I would stop eating for at least fourteen days and then I would take the drug protocol that we advocate because I know this would be my only chance of survival.

      And I know exactly what we have to do, how low we have to get the blood glucose down. But if you don’t need to do that, why would you do that? I know what to do if I had to do this. It’s like having the tire changer in your car, if you get a flat tire you know how to use it, but you wouldn’t just go out and change tires just for the sake of changing tires. I know what to do and we’re still working to it, but I think it’s generally a healthy thing to do anyway.

      Pauline Davies: Thank you.”

      More details here

      and here .

    • Tristan

      Peter and Paleo, thank you so much for your replies! I can’t tell you how much it means to have any kind advice right now – I can’t go to a doctor yet as my personal insurance policy just started on the 1st, and I’m terrified they’ll claim the condition existed prior to my coverage and drop me… but I digress.

      I did fasting HIIT the first two days of the diet, and have tried to stay moderately active since. I’m feeling better about energy and muscle loss now, but I still wake up with a blood glucose ~90mg/dL – higher than when I went to bed. I’m being very careful to not eat to much protein, nor too much at once, but… it’s hard to strike the right balance, I think.

      Peter, if you have time, I see that *your* blood sugar isn’t really much lower than “average”, even in a state of full-on ketosis. If ketosis doesn’t precipitate a drop in blood glucose, how is it supposed to deny food to glucose-hungry tumors? I’ve read that people on a combination of extreme calorie restriction AND keto can get the their blood glucose down around 50-60mg/dL for the purposes of fighting cancer, but those reports describe diets of 600 calories per day… with the associated side-effects. I’m not trying to play devil’s advocate, but it does seem to be a legitimate question.

      Again, thank you both so, so much for taking the time to talk with me. It’s been a very rough couple of weeks. :-p

      • Great question. It probably has more to do with insulin levels and IGF-1 than glucose levels. I do plan, in the next year or so, to do a very detailed series of posts on cancer.

    • Tristan

      Raymund, that’s a lot of food for thought – forgive the pun. Ugh, terrible… 😉 Thanks very much for those links; I’ll look at them in detail, but I wanted to give you my appreciation first. It’s very kind of you to show interest, and I hope someone else out there might eventually benefit as well.

      Peter, thanks to you again for taking the time. I’ll also thank you for a friend of mine who went keto after discovering this site and isn’t looking back. 🙂 I look forward to reading more here, cancer-related or no. Much gratitude.


    • Raymund Edwards

      Tristan , You can look inside that book on Amazon..

      He especially mentions caffeine in the form of Coffee as something that will not allow the blood glucose levels to fall . Even after 6 days of fasting and elevated Ketones.

      it is on page 381 .

      From Jimmy Moore’s Site –>

      “. Seyfried noted that a cancer-preventing fast should probably be done using distilled water only and nothing else”

      “A therapeutic fast should not contain any nutrients. The body will release vitamins from fat and minerals from bones during the fast.”

      “He explained that the weight loss on a one-week fast like this is mostly water weight because the fasting process depletes glycogen stores which retain most of the water in the body.”

      “Dr. Seyfried noted that there is some “minor” protein loss “especially if fat is mobilized”

      “If your blood ketone levels are elevated then you are definitely burning fat.”

      When I asked what this weeklong fasting does to cancer cells, he said the “damage to mitochondrial respiration is the origin of all cancers.”

      “Fasting will induce cellular autophagy thus allowing the cells of the body to consume damaged or defective mitochondria. Metabolism of ketone bodies will reduce damaging oxygen radicals while enhancing the metabolic efficiency of the mitochondria. Fasting prevents cancer by enhancing the metabolic efficiency of mitochondria and by eliminating damaged mitochondria.”

      “He recommended a book Herbert M. Shelton called Fasting for Renewal of Life that gets into the nitty gritty of what is happening when you fast.

      “He reiterated the importance of consuming only distilled water or a small amount of non-caffeinated green tea. As for the vitamins I took during my fast, he said they are “not needed for short fasts (less than 20 days).”

  • Alkarim Jina

    Hi Peter,
    Thanks for all the info. Have not parsed all of it. Also an MD via Canada, currently in SF. Am wondering if you have any thoughts on Ketosis and Altitude +/- Diamox. Have just recently embarked
    on the ketosis/low carbohydrate journey and exercise and am looking for shortcuts. Am going on a 5 day backpacking trip to Giant Sequoia and going to try and maintain my diet. Altitude ranges from 8,000 feet at the start sleeping in 10-12,000 range with a 14,000 peak over 4 days… Will be taking Diamox(never AMS but just want to try it) and NSAID- recent Stanford study with Iburofen. Of concern was that study with military that showed soldiers with 70% carb diet did better with less AMS. Wondering if you have any pearls of wisdom and really if should forgo ketosis/diet for this brief interlude. I understand if you won’t be able to reply in a timely or material manner.
    Many Thanks,

    • Funny you should ask. I just got back from a very intense bike training week in Colorado, which included most major climbs between 12,000 and 14,000 feet (including Mt. Evans). While anecdotal, I had heard that ketosis was a superior state for elevation. In my case, this turned out to be exactly true. I suffered no AMS, despite having no time to acclimate and felt shockingly strong at elevation, especially relative to others. While most of the riders I was with were much stronger than me, the gap seemed much narrower at elevation. Not sure what to make of it.

    • Alkarim Jina

      Thanks Peter,
      Update: Interesting experience, but too many confounding variables to tease out the most likely etiology which may just be simple and common. The week before I had gone backpacking, I had tried some Nattokinase/ Serropeptase which I noticed had a diuretic effect. I felt like I was in Ketosis formost of the day (just butter and MCT oil in the morning) and would use UCann with exercise-mostly cycling. I do notice I lack a certain oomph at what I presume anaerobic threshold but lack of fitness
      is also a variable.

      I wanted to try Diamox to see how I would do on it in case I went to higher altitudes and to see if it was advantageous. I started with 125mg BID 48 hours beforehand and increased to 250mg BID, 24 hours prior to driving to 8-9000 ft at Mineral King in Giant Sequoia . I did notice a diuresis, less appetite,
      a loss of a pound or two, and ate less. I increased added salt empirically and wondered if eating less would be beneficial… Upon arrival, I seemed to be adjusting well to altitude and less fatigued than my confreres(one a sports medicine doc from UCSD).

      The first day was a killer. Despite the lightest pack I have ever carried- close to 40 lbs., I struggled. I just didn’t have the legs, much like cycling up the first hill-no legs. A friend took some weight but the long day continued including a 1-2 hour grind up some scree at Sawtooth Pass which seemed more of an anaerobic endeavour. We went down to Glacier Pass and over to Silver Lake… I realize I was over normal fatigue but not anything I hadn’t done before. That night I started eating the pasta and couscous being cooked… The next day went better over Blacrock Pass into Big Five Lakes but still fatigued….

      About 24 hours post the first day exertion, I got myoglobinuria. Though tired, I didn’t feel that untoward nor particularly achy. ECF wise I seemed well hydrated, and had been sucking on a Camelbak all the way up the passes. That night I drank about 3 litres of water, ate carbs with extra added salt and stopped the diamox. By morning it had mostly cleared with some minor episodic discoloration. Over the next couple of days I continued to regain strength to about half. I didn’t know what to make of it, I suppose perhaps I was hypovolemic at least intra-cellularly, had been on a PPI-omeprazole, and was in a ketotic state at least the first day. I know they use diamox sometimes as a treatment for rhabdomyolysis probably just to avoid renal precipitation but confounding overall. I certainly won’t use diamox again unless necessary. Back at sea level, apart from normal fatigue, I feel fine and haven’t objectified any measurements, and back on my normal routine. Never had myoglobinuria before even at higher altitudes-highest being 20,000 ft. An interesting anecdote.

  • Scott B.

    August 30 19:16
    Ketone Help. I started LCHF 6 weeks ago. Immediately dropped 10 pounds and need to plateau as it continues to decrease. I’m super active cycling and working out 5 to 6 days a week.I got the meter and tested Glucose (out of curiosity)20 min after a meal sugars at 70, the next day (yesterday) tested Ketones mid day 0.3. Today I blood tested first thing in a.m. and Ketones are 0.6, which sounds very low. I appear to exhibit all the signs of being in Ketogenic state, no food cravings, frequent urination (which is decreasing, thankfully) was keeping carbs less that 50 per day, now somewhere between 50 and 100. Extra are pre, post and during more intense cardio. work (2 to 4 hours). I’ve definitely lost strength in regard to cycling, hoping it will return??
    What does low Ketone blood measure mean in regard to Ketogenic state?
    What other fats can I eat to avoid continued weight loss (I may be eating too much protein now?)
    And the big question, how does the body utilize fuels in an Anaerobic state if there aren’t adequate sugars availabe for fuel???

    Thask for any input…

    • Bill

      It would be interesting to hear how you fared. In theory, in a ketotic state, you don’t have easy access to pyruvate which would generate energy in the anaerobic mode, mainly in the circumstances of weightlifting and climbing long hills on a bike. How did time and more training play out for you?

  • Gayle

    Is the vitrgo s2 a super starch as well?

    • No. Only Generation UCAN has the IP to make super starch. Others just use amylopectin or waxy maize, but don’t hydrothermally treat.

  • Kim

    Problem: A pro-cyclist might burn 5500 calories in training everyday. Even if they’d be getting 80% of energy from fat, that still leaves 1100 calories from glycogen – daily. So how could a professional cyclist possibly be keto-adaptive?

    • A pro cyclist could likely tolerate more carb/protein to remain keto-adapted, given their enormous expenditure.

  • chris

    I just wanted to say thank you. I was inspired to give low carb/high fat way of eating a try. I raced on Sunday in Amsterdam (two weeks after changing my eating) and I had a great day full of energy, despite not eating any gel or drinking sports drink. It was tough to break through the sports-nutrition-dogma. But this method worked for me!

    • Wow, that’s actually unusual. Good for you. Most people do not adapt that quickly. I sure didn’t…

  • chris

    I should add the change was dropping carbs from about 100-150g/day to <50 and increasing the amount of fat. Moving out of the "wobble" zone has been very satisfying so far. I'm looking forward to seeing how this works for my 25k race next month, and next year's cycling season too. Thanks for taking the time to produce the superstarch video – really interesting and will help me explain this to my friends.

  • AT

    Hi Peter,

    I run the risk of oversimplifying things here, but doesnt the introduction of UCAN at least in theory ELIMINATE any sort of trade-off between aerobic efficiency vs top-end power? So you can be in ketosis but as long as you keep your glucose levels topped up using UCAN you can still be very competitive in lets say sprint or olympic distance triathlons which – lets face it – are at threshold for 80% of the race and above threshold for the remainder.


    • Yes, that was my original reason to start experimenting with it over a year ago. Could I get some of the glucose I was missing, without inhibiting ketosis…

  • AT

    So have you found that you have regained some of your top-end power after starting to use UCAN vs in the past when you relied mainly on ketones?
    Perhaps that could be a great experiment for the future – give a placebo and UCAN to a fully keto adapted athelete at two different sessions and test performance at threshold intensities

    • I definitely feel my top end is better this year than one year ago…but I can’t honestly say I know which factor or factors have contributed, and to what extent. If I had to speculate, I’d guess that adaptation has continued and I’m getting more efficient with less substrate. I think UCAN plays a role, but it’s hard for me to parse out exactly how much, because my metabolic state is already putting me a low insulin environment, so UCAN’s help may be just incremental in me (vs. more pronounced in others). Agree with your idea for an experiment.

  • Julia

    Hey Peter
    Forgive me if you’ve covered this but I am still unsure of the way ketones reflect fat loss. If my blood ketones are low (.2-.4) could I still be burning fat?

    Thanks for all you do!

    • Yes, one need not be in ketosis to burn fat. Ketosis just means you’re produce enough B-OHB to offset your brain’s need for glucose.

  • AT

    Hi Peter,

    My question is in regards to how long it actually took your body to adapt to a high volume training regime while making the switch to a keto-adapted state. I am asking you for the following reason:
    I’m in my first month of keto adaptation, and made sure it coincided with my off-season in triathlon to give my body a chance to make some adaptations “at rest” before starting to build up volume again.
    Last week I went for a 4hr fun ride in the mountains, it was my first long ride since starting the new diet so didnt really know what to expect. I was happy to find my energy levels steady (just one LCHF bar during the ride and some nuts) though I found my climbing power to be absolute rubbish.
    Today I went for a low intensity/aerobic 80 mile ride on flat terrain. It was going great for the first half with no hunger or need to refuel and somewhat decent output but after the 3hr mark the wheels started to come off. I had another LCHF bar and kept replenishing with water which got me back home through another 1.5hr of being in a very fatigued, low energy/cursing my existence type state (couldnt just stop cause I was another 30 miles from home). Once I got home I could hardly stand up without getting dizzy and found it hard to even take a shower while standing or cook my post-workout meal. Please note I had 400mg sodium before the workout and another 500 or so during.
    Once I ate my post-workout meal (LCHF) I immediately felt better but I still felt a bit “off” for the remainder of the day.
    What has your experience been when starting out? I may have gone a bit too hard on cold turkey here so will try to take a bit more fuel with me next time but did you find yourself feeling like this sometime in the initial phase? Will it gradually start getting easier? Maybe I was too low on sodium? Anyone else had any similar experiences?
    Apologies for the long post

    • It’s been so long now, that I’m sort of forgetting, but I think it took about 12 weeks to really adapt. Maybe even longer to get the last 10%.

  • Michael

    I am trying to get me head around what you are saying about higher glucose levels and lower B-OHB levels after a high intensity workout. When I do HIIT my glucose levels rise about 75% post workout from pre workout. My B-OHB levels post workout are relatively low (0.3 to 0.6). Does the fact that there is hepatic export of glucose during high intensity workouts mean there is an elimination or significant reduction in ketosis, and if so for how long? Or are both happening simultaneously? In contrast when I do a moderate bike ride (65-70% of max heart rate) my B-OHB levels usually are a full point higher than after a high intensity workout. Does the low level of B-OHB (sometimes <0.5) after a high intensity workout mean that I am not fully keto adapted or is it a function of the intensity of the workout. Or both?

    • Yes, HGO raises overall glucose levels, which raises insulin levels, which lowers B-OHB. How long this lasts is not entirely clear, but it seems to be dependent on duration of exercise, intensity, and maybe a few other factors.

  • Lisa

    Firstly, thanks SO MUCH for the hard work you put into his blog! The amount of information here is staggering and I’m only beginning to scratch the surface. A percentage is somewhat over my head but when I put in the effort, I learn a lot.

    My question is a little off-topic for this thread but it relates to something you said above:

    “Furthermore, the stress of a workout like this results in my adrenal glands releasing a set of chemicals called catecholamines, which cause my liver to export even more of its stored glucose via a process called hepatic glucose output (HGO).

    [As an aside, one of the major defects in type-2 diabetes is the metformin, used often in type-2 diabetes, blocks this process.] ”

    I have been in constant ketosis for a couple of months now and the transformation in my health is ASTOUNDING, energy, mental clarity etc. I’m convinced this is THE way to go! After having had a myriad of vague health problems that so often plague 40ish women, I now feel decades younger.

    The question is: a friend mentioned he is on Metformin to promote and support longevity. I can certainly see the theory in this but if I understand correctly, it seems to be a vague substitute for the conditions created by a ketogenic state. ( I would assume that if someone who was in ketosis took metformin they would experience a potential hypoclycemic crisis?)

    Am I correct in the (simplificated) understanding that a healthy, non-diabetic person taking metformin may assert some protective measures against glucose/insulin effects in the modern north-american diet so therefore it has at least some similarity to being in ketosis? I instinctively feel that ketosis is a superior state but I’m not sure I could explain why.

    Thanks again!!

    • Great question, Lisa. There is strong epidemiologic data suggesting that “prophylactic” use of metformin (i.e., someone who is not T2D but takes it) may be protective of several diseases, including cancer. In fact, I know a number of non-diabetic cancer researchers who take metformin prophylactically for this reason. Of course, no RCT data support this, but the mechanism does make sense, if you believe that more HGO leads to more insulin and IGF.

  • Maryann

    My husband and I were prescribed Metformin for preventive reasons by a cutting-edge lipidologist. after our NMRs. We were both prescribed 2000 daily. He is taking 2000; however, I had such horrible side effects that I stopped taking it. (We are taking the best brand for minimal side effects, so changing brands won’t help.) I was wondering Peter, if in your experience, there are people who just can not tolerate it. I started with a very low 250 and was instructed to increase gradually, but even at that level side effects were terrible. Our doctor who you know and respect, takes 2000 per day herself for prevention. I think it is important to take it. I was wondering, not in my personal case, but in general, if you have seen this problem and what the cut-off point is with patients who have persistent side effects…how long to give medication a try and at what point the patient is determined to be intolerant. I am aware of the many benefits you mentioned about metformin. Thank you! maryann

    • I do know that some folks can’t tolerate it, with nausea being the most common side effect. One option, if your doctor feels it’s helpful, would be to reduce the dose to 1000 mg. I’m not sure the drug has any efficacy below 1000 mg, though maybe ramping up could help.

  • Maryann

    I’m at 250, but thanks. You’re right, efficacy is at 1500-2000. I was just interested in knowing at what point to give up trying…how long to wait before expecting side effects should be gone. Thanks again for your kind help.

  • Dave_B

    Hi Peter – Thanks for all this great information.
    I’ve regularly been in ketosis for the past couple of years and recently invested in a blood ketone meter. I conducted an n=1 experiment recently to figure out the amount of fat I can consume withouth significantly affecting my post prandial triglyceride levels. I’ve posted about this experiment on the Track Your Plaque forum if you have access :
    Briefly, I measured TG’s, blood ketones and blood sugar, upon waking, 1 hour, 2 hours, 4 hours and 5 hours post “breakfast”. Breakfast consisted of 25gm LEF Whey Protein, 5gm psyllium husk, 8oz water and 45gm of “high oleic” safflower oil, coconut oil, butter or olive oil.
    The results surprised me. Safflower oil had the least effect, followed closely by butter. I noticed that as my level of ketones increased so too did the TG levels – mild exercise seemed to reduce the levels after a period and I wondered if you’ve noticed anything similar i.e. your exercise prevents negative effects of higher TG’s.
    I’m planning on repeating the same experiment using MCT oil, almond oil and high oleic sunflower oil.
    I’m regularly in and out of ketosis with eating 60-80gm carbs – I wondered if you consider it likely more beneficial to stay one way or the other rather than flip-flop between the two?


    • Very interesting results, Dave! Thanks so much for sharing. I wonder, exactly, what is going on? The MCT will likely increase ketosis, but I do wonder about the impact on TG. PLEASE do keep me (us) posted. BTW – what did you pay for your TG meter?

  • Dave_B

    Hi Peter- I’ll keep you posted. The next series of tests will most likely be early in the New Year. I just placed an order for the TG strips. I use a Cardiochek PA meter which cost me iro $600 five years ago. The results have generally compared well with lab results and I’ve found it useful to be able to test my cholesterol on a weekly basis to help assess dietary changes. There is also the regular Cardiochek meter which now retails for around $90 and is probably just as good as the professional version when it comes to testing individual levels i.e. TG or HDL or total cholesterol. I purchased mine from but they do come up regularly on ebay at good prices. Cheers!

    • The only thing I’d want to check is trig, so looks like the $90 version + trig strips would be good.

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  • Dan

    I am on day 35 in ketosis and it is awesome, my experimenting has lead to a full life change. I am finally at the point where I can pick up the speed again. My running tests have all been fasted and I laugh the whole run in amazement; it is incredible. The other day I ran a 21 mile run with about 3,500′ of climbing. Three hours into the run I had a Stinger Waffle, I was also told that I could eat a carb or two mid run and wouldn’t kick me out. Once it hit my blood, I felt like a rock star and had an awesome kick for the last mile at 6:40 pace. This is not typical for a training run.

    I am running a 10k this weekend and want to go full throttle. My gut is telling me to eat a gel or something prior to the race. I feel that I will have plenty of carbs stored, will I? I was suggested to eat a full 50g of carbs the night before including a sweat potato. I am planning on running under 40 minutes and my heart rate will be maxed.


    • Dan, let us know how it works!

    • Dan

      Well, I was talking with my buddy the night before the 10k and he said that I have enough glycogen stored in my muscles to last me for at least 1.5 hours, so I didn’t eat a gel. But since I was peer-pressured to run hard, a ‘friend’ placed a bet on me – thanks buddy, I didn’t think it was enough. So 60 minutes before the race I had an espresso (typical) and 30 minutes before I drank a UCAN cocktail. Now I felt for this short of a race, the UCAN might not influence my performance, but I didn’t think it would hurt me. I guess it was mostly psychological. Also, I did have a yam with dinner the night before, still maintaining my 50g carb limit.

      The Results: I ran 40:22 which is 4.5 minutes faster than last year’s 10k; I have only run two 10ks ever. I am 42 years old and only been training (running) for two years now. Hmmm, so many variables? The Wednesday before, I had a gym workout that really beat me up. It didn’t seem hard at the time, but I felt it right up to race morning. I took three ibuprofen (not typical) prior to the race; that is how sore I felt and also shows how smart I am. The first thing I noticed, which was not typical, was that I did not have a finishing kick at all and I always have a kick – a strong kick. Aside from the first mile, which was a bit fast, my pace was the most stable ever, which also could be the reason I did not have a kick. I don’t think that taking a gel would have improved my performance; in fact I would bet that I would have had a slower time due to a fluctuating pace. It is hard to say.

      I have a 5k coming up in a week and haven’t run one since high school without a pushing a stroller. I plan on eating a yam the night before and an espresso morning of. I am shooting for a sub 19 . . . we will see.

      • You’ll go under 19 with the right speed work. 800 meter repeats are your friend.

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  • Monica

    I am 48, I’ve been eating more or less Paleo (about 85%) for the past two years and am on day two of VLC. My hands and feet are swelling quite a bit. I always have some pitting edema in my legs by the end of the day, but generally my rings are loose, however, they started feeling a little tight yesterday and are appreciably so today.
    I’m using to track my food, and according to it I’ve had 21g (4%) of carbs, 1417 mg of Potassium and 2530 mg of Sodium so far today. I workout 5 days a week, Crossfit with a strength emphasis.
    I drink one large coffee with heavy cream every morning, and nothing but water for the rest of the day. Do you have any idea what would be causing this?

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  • Indy M

    Finally got ‘Keto adapted’ (about 2.3 on the Meter today) after ~3 weeks of <= ~40 gms of Carb/day. After a few days, I want to introduce UCAN(10-20gms) for Dinner, in a soup, and see if that takes me out of NK. I have been trying to incorporate UCAN into my regular meals and increase my hydration at the same time. If it does not take me out of Ketosis, that will be a big help and a big find! (Don't like to cook at night ;)).

    Indy M.

    • Keep us posted. Remember, though, you can’t heat the UCAN product or the hydrothermal processes reverses and the superstarch reverts to just plain old waxy maize.

  • Indy M

    “Peter Attia February 12, 2013
    Keep us posted. Remember, though, you can’t heat the UCAN product or the hydrothermal processes reverses and the superstarch reverts to just plain old waxy maize.”

    No, I did not know that. I thought I read thru the package material carefully enough. Many many thanks, I will try my experiments without applying heat to the UCAN powder.

    • Check directly with them. I don’t recall the temperature (maybe 110 F) at which it basically reverts to (now very overpriced) waxy maize.

  • Alex

    Hi Peter,

    Thanks so much for all this information!!
    So is it beneficial to use metformin while on a ketosis eating plan or is that something that will inhibit the process? All the warnings talk about diabetic ketoacidosis and not to use metformin but I know that is different than nutritional ketosis.

    Thanks again!!

    • It probably would make it easier, but that’s a speculation. It is by no means close to necessary.

  • Jo

    Hi Peter
    I am really enjoying reading through your website, I am a high performance endurance type athlete and trying out a Keto diet.. My dietician is not so impressed at this stage! Just wondering if you had done any research into the low carb diet and immune function? The main concern being that carbs have such a influence on immune function, and so by dropping the carbs, my immune response may not be good enough when flying etc.. Also was wondering what you thought about how having gels or high carb on race day only would affect the whole process?

  • Bob Poulson

    I have a question about pre-race diet. I will be running Boston in three weeks. I am on a quite strict LCHF diet and it seems to be working well – have been training hard and feeling good. The question is, do I maintain the LCHF diet all the way to the race, specifically two days and one day before (I eat almost nothing race morning – don’t like to have anything in my stomach)? Or do you recommend taking in a certain amount of carbs?
    Thank you.

    • Stay where you’ve been training. No sudden switches on race day.

  • Justin

    Thanks for providing all this info to us. Two things (1) I was on a 3 hr ride today and since I only workout alone, I tend to think a lot. So, I didn’t have a particularly good day yesterday carb-wise, about 250g. This morn, I had my normal no/low carb/ high fat breakfast. Only consumed a little H2O on the ride and had what felt like boundless energy. After burning off 2500+ cals on the bike, am I jump starting ketosis this way? Is this the right way to think about it? I have a blood ketone meter but am just hesitant to use too often due to price. (2) love that Richard Feynman was included here. I was forced to read “What do you care what other people think” as a ninth grade summer reading assignment. Well, it really forced me to think about things differently and was one of the most enjoyable reads of my life. So, kudos for including him here.

    • Hard to know what is going on. It would hard to be ketosis one day after consuming 250 gm CHO, I suspect. This would be a great time to do a check, despite the cost.

  • Graham

    Hi Peter,
    I have only started the last 8 days with less than 50g of carbs per day. I am on a week long training tri camp in Tuscany Italy. 6 hours on bike today, felt sluggish until stop after 4 hours then had some carbs felt like I was on rocket fuel the last two hours. Look forward to trying Ucan SS soon when I can get hold of it! Racing half Ironman on 19th May, hilly bike.
    Question is it possible to be in nutritional ketosis and use Ucan SS so you can start an Ironman race with full glycogen levels in your muscles, and still have the metabolic flexibility you speak of?

  • Tom Hughes

    Hello again Peter,
    I wanted to ask you a couple of questions that I am struggling to get answered, so I thought you could help.
    I have been on a ketogenic diet for a while, I was testing myself daily with a blood ketone monitor but it got a bit expensive so I stopped. I have been experimenting with getting in carbs here and there to try and preserve my top end so to speak. I am a triathlete but also road racing on the bike.
    I just wondered, firstly are you still in nutritional ketosis? How is it going? Are you still using the superstarch? Have you had any more physiological testing to see how you are on that front?
    I have been trying to boost my ketosis with MCT, mostly from coconut oil/creamed coconut. have you ever tried this? Do you know of any studies (or any personal experience) of using MCT based products to support ketone production in the presence of carbs?

    Also, I have noticed something odd. I tried a similar approach to the cyclic ketogenic diet, with a carb refeed on weekends. I mostly did this due to reading some worrying articles on the affect of ketosis on testosterone production and the resultant effect on testosterone/cortisol ratio.
    Anyway, I have noticed that the day after a re-feed my heart rate variability plummets and I feel awful. Have I made myself carb intolerant? Is this the result of pushing myself out of ketosis?
    I have just ordered a large batch of ketone test strips so hope to have some answers soon.
    Sorry for all the questions!
    Tom Hughes

  • Dave

    Hi Peter,

    Having been cycling long distances (40-70miles) for 3 years and ultimately gaining weight over that time, I found Phinney, Volek, Taubes and you and for the past month or so have been strictly LCHF and ketogenic, have dropped 10lbs, feel great, do not get hunger pangs etc…(still have some weight to drop btw).

    But I’m struggling with my cycling…if I ride at a high, but not exhaustive tempo, things are generally ok, I feel my legs are a little “heavy”, but manageable. However as soon as I need to push it (hard effort on flat/rolling terrain, or a long sustained climb – gradients of 6% and higher, up to as much as 17%), then I just seem to lack the energy to sustain that effort.

    I dont take Mg supplements, but make sure I get enough sodium, but I wonder if an almost complete lack of CHO is failing me on these efforts and whether I need to think about taking carbs before and/or during my rides?

    I really believe in the science of this LCHF lifestyle, but I have doubts due to a couple of rides where I just didnt feel “up to par”…yet your scientific approach seems to suggest I’ve got something wrong… do your legs “feel” when tackling sustained effort like climbs of 6-8 miles?

    do I need to give it more time?


    • Impossible for me to troubleshoot without spending time with you, which I can’t do. If the issue is not one of sodium, potassium, magnesium, or hydration it seems like you (as was the case with me) need more time to adapt. This literally means your muscles need to re-train to be more reliable at oxidation (vs. their preferred state of glycolysis). It will take a while. For me, 3 months to feel pretty good. Two years to feel better than ever. Worthwhile investment for me, but a personal decision for everyone.

  • Fabian

    Hi Peter,

    First of all I’d like to thank you for the informative blog you brought to life. the amount of information is enormous.
    Second, I have a question, to which I could not find an answer for so far.
    I’m genetically pretty lean with a pretty fast metabolism. 6 Months ago I started weight training (to put on some weight preferably in muscle) and went from 141 lbs (11% bf) to 162 lbs (16% bf)
    Naturally, I developed a little pot belly which now I’m trying to get rid of. (That’s how I stumbled upon ketosis and therefore your blog)

    My BMR at the moment is at 3400 kcal a day. If I would go with a ratio (a figure I have from another place) of 60% fats 35% proteins and 5 % carbs. I’m obviously way over 120-160gm of proteins. (about 300gm)
    I’m unsure how to ask this correctly cause English is not my native tongue. But what I’m trying to ask is, if I can ever reach ketosis with a percent based approach, or are the 120-150mg of proteins a (more or less) a fixed value. Would in my case something along the lines of 80% fats 15% proteins and 5% carbs the better solution? 80% (302gm) fats just seems to be a ridiculous amount to me.
    I realize that you can’t give a definitive answer to my question, as obviously no two people are the same. I’m just looking for a pointer to what makes more sense. Percent based approach or strictly control the amount of carbs/proteins and the fill the caloric deficit with fats.

    Thanks again for your awesome blog.


    • Can’t troubleshoot with any value over blog. But if by “BMR” you mean basal metabolic rate, 3400 would be really high. If you mean “TEE” (total energy expenditure), that would make more sense. I prefer the terms REE, TEF, and TEE (as described on the blog).

    • Fabian

      I’m Sorry. What I was trying to describe is in fact what is described as TEE in your blog. I have obviously not yet managed to read all of your blogs. So on a training day I “need” about 4300 Kcals and on a normal day 3400kcals. If I go below these numbers, I definitely lose weight rather quickly.

  • Sid Mascetti

    I’d like to sincerely thank you for sharing your ‘n=1’ study. This was exactly what I was searching for. 🙂

  • Kevin


    I have been on a Ketogenic diet for almost 6 months now and it has changed my life. I am down 47 pounds with about 60 or so to go. I am working with a great doctor at SpecialtyHealth in Reno who is very supportive of my plan and keeping an eye on my blood work and lipid panels including the NMR LipoProfile (86th percentile in insulin resistance). I supplement daily with a multivitamin, 600mg potassium, 400mg magnesium, 2000iu vitamin D and 1000mg fish oil. I for the most part am very strict on my diet with no cheat days. I even avoid all artificial sweeteners because I wanted to completely lose the taste for sweet.

    For most of my time on this diet I did not exercise. My weight, lethargy and even depression made it so I had no interest in it. During that time I found that I had no need to supplement sodium. I love salt on my food and it has seemed to be enough. Over the past month I have stopped salting food (after preparation) in an effort to reduce blood pressure. My doctor mentioned there is conflicting opinions on the effect of sodium on blood pressure and exercise along would probably get my blood pressure in place. I wanted to perform an N=1 on my self and see if reducing my salt intake would lower my blood pressure (without exercise) and it did. It appeared to have taken me from pre-hypertensive to normal. Even without the additional salt on my food I still felt great and did not feel the need to supplement sodium. Recently I have started exercising in the form of mountain biking. Three days ago I rode 11.5 miles on a relatively easy trail. I felt great with lots of energy and finished even stronger than I started. Since that time I have really slipped into feeling bad with no energy, yawning throughout the day (which I never do anymore and definite “brain fog”. I feel so good most of the time now that feeling this way is horrible. It took me until today to remember the sodium supplementation and to me it made perfect sense with the introduction of the exercise. I took 2mg in the form of bouillon and already feel much better.

    My question is does this make sense that I have just reached a level of exercise to require supplementing sodium or should I have always been doing it? Is there a way to gauge how much to supplement other than the way you feel? Also I wondered if the vitamin supplementing I am doing above seems appropriate or if you had any other suggestions.

    Thank you in advance for your time and and for also being the architect of the lifestyle change that is turning my life around after i’ve tried everything else and failed.


    • Hard to know, Kevin, without doing some blood work, though sodium needs can largely be addressed by “feel” — if you feel light-headed, you likely aren’t getting enough. Similarly, cramping is usually a sign for more sodium and magnesium (the potassium often takes care of itself when these two are corrected).

    • Hard to know, Kevin, without doing some blood work, though sodium needs can largely be addressed by “feel” — if you feel light-headed, you likely aren’t getting enough.

  • Hemming

    Hi Peter,

    In case you haven’t seen it, Ben Greenfield has a great podcast with Jack Kruse on performance on a very low carb diet. He covers a lot of different topics and I guess he could for days on each of them. Basically his view is that you can perform at the highest level on a ketogenic diet but you need 24-36 months to adapt (and then add the cold thermogenesis). Jack Kruse’s blog must be right up your alley too 🙂
    I’m not saying he is right or wrong but it’s at least some very interesting views he has.

    • In my experience, there seemed to be a real turning point in my anaerobic capacity about 18 months in, so I think there is something to the idea of long-term adaptation that goes well beyond the short term adaptation.

    • Hemming

      Really interesting. I’m hoping for more info on that in part 3 of this series. Do you still eat around 100g protein/day, 20g carb/day and the remainder in the fat or have you tweaked the levels a little?

      • Lots of tweaking. Heavily dependent on training and travel schedule.

  • Mark

    I had a question about how alcohol fits into the scheme of blood lipids and CV disease especially the belief that alcohol has a protective effect and this seemed like an OK place for it since you reference Gary Taubes article that includes the “compliance effect” in this essay.

    The first mention I ever heard of alcohol consumption having a heart protective benefit was an old 60 Minutes segment on “The French Paradox”. That Paradox turns out to be the fact the french have lower rates of CV issues even though consume a relatively high fat diet….which we all know causes heart disease, hence a “paradox”.

    Obviously the alternative hypothesis would hold that this isn’t a paradox at all, it’s just evidence the premise is wrong. They go on though to decide that french moderate consumption of alcohol has a mysterious protective effect against their obviously heart stoppoing fat laden diet.

    Since then this line has come to be widely believed.

    Perhaps you can someday do a piece about how alcohol is metabolized and how it fits into other issues.

    I had the notion recently that the “compliance effect” that Taubes writes about as a major confound may explain much of the supposed protective effect of alcohol.

    It seems a good guess that “moderate alcohol consumption” may be a pretty good marker for “high compliance effect individual”. People who drink immoderately are probably not high compliance and people who don’t drink at all may be either recovering problem drinkers or people with an undiscovered propensity for it.

    “Moderate drinkers” may correlate pretty strongly with the sort of high compliance person who has better medical outcomes either with the treatment or the placebo.

    Otherwise the French diet fits with your essays about asian diets. It’s not historically very high in sugar which is the main factor whose consumption increased in parallel with metabolic syndrome and obesity.

    I’m also wondering about how closely related alcohol and fructose might be in long term effects on the liver and all that complicated biochemistry the liver does.

    • Yes, I need to learn more about this topic. At least two separate issues confound it: 1) the CHO content of some alcoholic beverages; 2) the specific effect of EtOH on the liver, independent of point #1, and how that impacts VLDL production, etc.

    • Maryann

      Hello, Mark and Peter, a very detailed and enlightening discussion of this topic is part of Dr. Lustig’s presentation “Sugar the Bitter Truth”.

  • Mark

    Thanks MaryAnn, I’ll check it out.

    On topic for Ketadaptation and exercise I just went through the excellent explanations again of ATP pathways, super starch and endurance exercise. Great stuff.

    If I follow it correctly it seems to have implications for the much larger group of people interested in metabolic syndrome, obesity and exercise. It seems to imply that for ordinary pretty unfit people with too much fat, that aerobic exercise will have different effects in people with ketoadapted metabolisms than with glycoadapted (or whatever ya call it). If I’m not misunderstanding, ketoadaptation ought to produce a faster rate of fat loss and perhaps more rapid improvements in aerobic exercise performance for the same levels of exercise than would occur with glycoadapted people, especially where both are on non-calorie restricted diets.

    This may be another variation on experiments contradicting the “calories are calories” paradigm that might have unambiguous results.

  • Jessica

    Dr. Attia,

    Was wondering if you can discuss Metformin and how you feel about the addition of this drug? I started using it a few months ago and I have to tell you it has greatly helped in how I feel after I eat. And I am super super sensitive to carbs. I can tell fairly quickly if I’ve eaten too many about 30 min after I’ve eaten – even if I haven’t had a grain…I can feel the insulin response. I can tell that my insulin has risen. The addition of just 500 mg of Metformin has really helped squelsh that feeling. I really really try to watch grains, carbs, sugar etc. Sometimes I will have an insulin response after eating veggies or a salad and I even cut out balsamic vinegar b/c I thought that was what was causing this response. I do better with olive oil and red wine vinegar. I’m PCOS and wanted to come off of YAZ as i’m approaching 40 and I just was afraid of what would happen if I did. So I added the metformin. I can’t tolerate more though. I tried to up it to 1000mg and my digestive system can not handle it. Just wondering what your thoughts are. Again – have about 20 pounds to lose. My BP and cholesterol are all great. BTW I did a search on your blog for Metformin before posting this comment and only found one mention of it. If you have discussed just point me in the direction. Much thanks – Jessica

    • Jessica, it’s certainly a reasonable drug for some patients, and I’d prefer it over other oral agents used in T2D. As you note, though, the side-effects can be troublesome for many. Perhaps the ER version? (ext release)

  • Anyone (Peter or other) found about how much MCT Oil one can consume for 8-12 hours without experiencing GI distress during moderate to hard exercise? Just checking to see if anyone else has done the trenchwork before I go do it. 😉

    • Ben, VERY person dependent/specific. I can do 30 mL with ease, with our without BP coffee. 45 mL I’ve gotten away with, but not always. It basically depends on how quickly I can turn it into ATP. If very quickly, I’m ok; if not quick enough, I get GI distress. Lesson: start slow.

  • Frédéric

    Hi Peter,
    Have you noticed (for ex. during your bike rides) any changes of your heart rate for the same speed/power since you are keto-adapted and during your transition period.
    I am reducing slowly carb (though I am not in ketosis) and I have the feeling that my RQ is changing (for ex. no carb during my rides and no bonking) but my HR is slightly higher. Then in this case I am wondering if I don’t waste the benefit of a better RQ with a higher HR…

    • I think so, but there are so many confounding variables, I can’t be sure. Fitness, hydration, etc., all play a significant role.

  • Sherry

    I was talking with my sister who is a cardiology nurse at Mayo Clinic and she freaked when I told her about the consumption of fats, protein and carbs. Her first comment was, do you know what this is doing to your kidneys? Is she confused about what eating too many proteins will do compared to what being in ketosis will do to the kidneys?

  • Stella

    I have 2 questions regarding athletic performance & ketosis:

    Will being in a state of ketosis help increase performance in underwater hoceky (Yup, it’s real: The first 2 min of this vid will give a good indication of intensity and gameplay, if you’re interested: )?
    Will it help with post-exercise recovery?

    From what I’ve read it seems the answer is no or slightly though my understanding of this topic is not yet where it should be. I intend to experiment (guinea pig = me).

    Game description:
    A weighted puck is pushed along the bottom of the pool by people wearing fins, masks & snorkels. No scuba gear allowed. One of the keys to great play is an excellent breath hold. Even a slight increase in bottom time would yield fantastic results in a player’s contribution to the game. A quick recovery on the surface (taking 2-3 breaths instead of 5-10) would also make a player more effective. So I’m really keen to sort that out.

    Would a state of ketosis help me get a few extra seconds? From the definitions & explanations I’ve read underwater hockey is anaerobic and we certainly spend a lot of time in Zone 4 & 5. So no, ketosis probably won’t help. But what confuses me is that the VO2 seems to come down. And your performance at high altitudes has improved. Would that help in this situation or is it irrelevant?

    Typical game time (tournaments): 20 – 30 min
    Game time (weekday practices): 60 – 90 min

    My second question is would ketosis help with post exercise recovery? Weekday practices are Mon, Wed & Thurs nights. On Thursdays my in-game performance is down (subjective observation: I feel tired, can’t out-swim people as often and bottom time is shockingly bad) and on Friday mornings I struggle to get out of bed and am physically tired for the rest of the day.

    When do I have an “empty liver” and what’s a good way to fill it up again without going out of ketosis? Where can I find more detailed information on starting this diet? I’ve read the “How can I lose weight?” but I need a bit more info because as soon as I try to implement step 4 & 5 I start feeling irritable, hungry, I bonk and start craving sugary foods.

    Thank you so much for this blog. It’s incredibly informative.

    • Stella

      Am I correct in saying that your O2 consumption went down during exercise? Does that mean that you would enter the anaerobic cycle later and exit it faster? If so, does that mean being in ketosis could give me a few extra seconds underwater?

      I’ve been reading more posts on your blog. My questions about going into the diet have been answered.

      • Yes, appears O2 consumption decreases, which may also explain the altitude adaptation I spoke of in other posts.

  • Vanessa

    Hi Peter

    Great article, it’s fun to read others self expermentations.

    I was wondering, what do you use to check your blood glucose, lactate and B – OHB levels? I’m a nutritionist student and I’m very interested in this subject.

    Thank you for sharing your knowledge and experience, it is very useful for all the curious brains out there!

    • Precision Xtra.

    • Vanessa

      Thank you! Feel free to let me know if you have any interesting ideas for nutritional experimentations, I and my fellow students will have a go!

  • SteveK

    You know the breakdown of your carb / fat energy usage during exercise because you have been tested and know your RQ at various VO2 levels. For those like me who have not been tested, is there a simplistic equation that shows the general relationship between %VO2 max or %max heart rate and RQ so that I can know, approximately, the % of carbs and % fat that I am using at a particular effort?

    • These numbers need to be measured. See post/video on Quantified Self.

  • Estevao Jorge

    I’m a 40 years old runner. And im on ketogenic diet for a month now.
    The problem is my heart beat is too much increased during my workouts.
    Since i started this diet, i’ve notice a increased heart beat, at beggining making me stop the trainning. So, i give some time to complete the ketoadaptation. Since im in ketosys almost three weeks now, i wonder why this dont get better. Im checking my ketonas level and usually in the morning is 1.0-1.2 mmol, and in the evening as higher as 2.0-2.5.
    Usually my heart beats doing interval trainning like 5×1.000m stays in the 168-175 range, and now 200-230.
    And besides the higher heart beat i dont feel any symptoms.
    Even in the long run where usually my heart beats stays in the 145-155 range, now goes up to 200. This is normal in the keto state???

    • Hard for me to troubleshoot, but makes me wonder if you’re deficient in sodium (i.e., unless you’re deliberately supplementing sodium, you will be), which in turn leads to depletion of potassium, and possibly magnesium. If sodium supplementation didn’t fix this, you should see your doctor.

  • Emil Hjorth

    Thanks for an amazing post.

    I cannot get my B-OHB level to increase during exercise.

    I fast 16-18 and and normally work out fasted, I have a great amount of B-OHB (2-5) measured with ketosticks when measuring in the morning.

    After reading your blog i decided to supplement with BCAA 10g during fasted exercise, and experienced a drop in B-OHB levels immediately after training and several hours later. Tried dropping BCAA to 4-6g instead, but experiencing the same.

    Maybe i misunderstood a part, but as far as I understand, even though BCAA increases glucose this happens in a way that should not kick me out of ketosis right, since they contain no carbs, and the amount is very small, so it has nothing to do with the amount of protein.

    I Just ordered some MCT oil, and thinking about replace BCAA with MCT post workout.

    • 1. Not all exercise increases BHB (assuming one is starting in ketosis); depends on energy demands. Steady aerobic activity at ~60-70% VO2 max appears “best” for this effect.
      2. BCAA are consumed (read: should be consumed) in tiny doses, that it should little impact on ketosis.

    • TS

      Good day, Emil! I hope it’s alright if I give you my take on this.

      BCAAs pre-workout inhibit the muscle catabolism that would occur during completely fasted training and promote muscle protein synthesis. Of course, you’re still going to have to consume a source of “whole protein” after working out for MPS to eventually fully occur. The BCAAs just “flip the switch” more or less, but don’t provide the raw material for new muscle to be built.

      The reason that BCAAs suppress your BHB levels is because of the insulin response they cause; this is of course largely dose-dependent, but I would assume the insulin response is more acute rather than long-lasting. Still, I don’t think ketosticks offer nearly enough granularity that you could gather precise data about this.

      During anaerobic exercise your blood glucose rises due to your liver releasing glucose into your bloodstream and your BHB levels will fall because of the glucose and/or insulin This is why you might note lower BHB levels after a workout . Consuming MCT oil would certainly right away raise BHB, but here’s the thing: just because your BHB might be low does not mean you’re automatically in a state of low-energy, because remember your blood glucose is still going to be elevated for a while. For this reason I don’t think it’s needed to take MCT oil post-workout in the way that someone that is hypoglycemic should eat a bagel. Make sense? Personally, I’d just eat something and go on with your day and soon enough your BHB will go back up as your blood glucose normalizes. Some people consume MCT oil before exercise in an attempt to increase their performance, but this is not something I’m familiar with. Although, on the subject of BCAAs and MCT oil, your decision to take one shouldn’t per se affect whether you take the other since they’re so different in their effect.

      Also, if you’ve read the blog post by Peter from last year where he discusses his diet, you’ll note his observation that when he would consume his daily food intake in one sitting it would often knock him out of ketosis for a while (due to the insulin from the carb and protein load). You have to ask yourself, “should eating one meal a day be avoided for just that reason?” In my opinion that wouldn’t necessarily make sense.

      In essence, what I’m trying to get across is I don’t think the goal should be to have as high BHB levels as possible at every moment of the day, but rather taking note of your energy levels and how good you feel to guide you.

  • Emil Hjorth

    Good Day TS,

    Of course it is alright, – I am just glad there are so many knowledgeable people on this site, all interested in helping out and cracking the code for optimum health and performance.

    Sorry for the long post now, but it is hard not to make it in to a good discussion when the possibility is there to learn something.

    I tried to read most of the articles on this site, and read “Low Carbohydrate Perfomance” and several other sites regarding the subject, but it is easy to get confused with all the different studies, and a large flow of information sometimes with contradicting pieces. – I recently read a blog post regarding BCAA in fasted workouts and why it could be detrimental. Would love your take on that, the link is here:

    You might be right that Ketosticks don’t offer precise enough results to rest the case, I will have to wait for my Ketometer to show up in the mail (We don’t have these in Europe it seems) – If we assume that they are a just a tidy bit correct, it took about 24 hours until the ketone production was in the 1.5-3 range again after consuming BCAA on 2 different occasions.

    I read the first of Peters posts regarding what he eats, and even though I fast 16-18 hours, I manage to get 2 large meals, and until now none of them seem to have kicked me out of ketosis, even with up to 100g of protein in one sitting – the carbs though are never beyond 10 grams in one sitting though.

    I have always tried to maintain the optimum Ketose range for as long as possible to reap the benefits, but your post gave me something to think about, and moved my focus from maintaining a moderate/high BHB level, to instead notice how I feel and perform. And I guess as long as the carb restriction is still taking place, I receive all the benefits of the diet/lifestyle right?

    I think what confuses me sometimes in my quest for the perfect path to eating, and life, is that there is a difference in most NATURAL in regards to human evolution and health, and the most OPTIMAL situation regarding, strength, performance and health, and maybe these paths aren’t always the same?

    Since a caveman would never have access to BCAA, MCT oil or would have to supplement his daily grok food with 2g’s of sodium, even though he would most likely always be in ketosis?

    I guess the human body and the evolution is not for creating super humans, able to gain muscle, lose fat and perform like a beast in every possible situation. Instead built for the ability to keep the species alive and re-produce ourselves?

    Thanks again for your reply.

    Greetings from Denmark

  • Adriana hagidemetriou

    Dear Peter,

    I found out that I had insulin resistance almost 5 years ago (I also have PCOS and I May have thalassemia (which could not be concluded) , now although i had managed to shed weight and it may seem that my body is functioning normally, I have some concerns about the education around insulin resistance. I have only just started re-visiting and re-educating myself on this & I must say finding your blog, TED TAlk and NuSI site have been an absolute godsend!

    there is so much you have opened my eyes to, and although sometimes I need to read an article about 5 times to understand it, I feel I know more and so much better equipped to fight this and have started my blog to track my own findings…

    I have two main areas of concern.

    1. The prescription of diaformin/Metformin (which I have been on for 5 years now – and whom the endocrinologist says I must be on for the rest of my life (Which both concerns and frustrates me) whats your take on treating insulin resistance with diaformin/metformin? I really dont believe in it and want to wean my body off it but i am fearful of putting on weight as my body has become use to the help of this drug increasing my sensitivity to insulin, have I destroyed my metabolic system by being on this for so long?

    2. The types of excersise one should do if they are insulin resistant. Now i’m not sure if i’m interpreting this right but it seems as though High intensity work outs actually increase glucose in the body thus being less beneficial to someone with insulin resitance . Thus is it better to do low intensity workouts in order to keep glucose production at bay (in the beginning of my diagnosis I was only walking first this in the morning before eating and thats all the exercise i was doing) and i managed to drop so much weight.

    Now however , I have gained weight (but still at normal weight range) but i am going to the gym almost everyday, lifting weights but also doing high intensity workouts, however I don’t seem to be budging in weight)

    Could there be a relation between the intensity of exercise and glucose production ? and which is best for someone with insulin resistance?

    I understand you are a very busy human so ANY guidance would be greatly appreciated.

    Also if you are reading this I just wanted to thank you for giving hope that there is a greater science out there, one that explains the WHY and the HOW and doesnt mask the proxys but treats the underlying issues!


  • Karl Ulrich

    Dear Peter:

    Amazing blog. Thanks very much.

    I’m puzzled by something.

    1. You and others have asserted, and it’s certainly widely believed, that those on calorie-restricted low-carb diets initially lose “water weight.” I believe the logic is that the body first makes up its energy deficit by consuming the glycogen in the liver and muscles, and that this glycogen (say 500g) is bound to a lot of water (say another 1500g).

    2. But, you’ve also written (and cited studies) showing that glycogen is still stored in the muscles even under ketosis, presumably from glycogen produced by the liver from whatever carbs are consumed and whatever else it can scavenge. Presumably with even a few hours of calorie surplus, glycogen stores would begin to be recharged.

    I’m not sure I understand how both of these mechanisms can be reconciled. In sum, how can there both be “water loss” and replenishment of glycogen on very low carb diets? Is it that glycogen stores are only replenished under ketosis when and if the body has a calorie surplus? Does that calorie surplus have to persist over days and weeks? For instance, is it that “Biggest Loser” contestants will never replenish glycogen until they stop running huge calorie deficits; they always have empty tanks? If so, can a cyclist never both have a full glycogen tank and be trying to lose a few pounds (my situation)?

    • The water loss is mostly plasma water loss. Glycogen loss occurs, but it probably rebounds to about 2/3 “normal” levels. The latter is a tiny amount of weight. The former can be more significant.

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  • Dean

    Hi Peter,

    I have enjoyed reading your blog and I am trying to figure out the best nutritional protocol for keto running/training. I’m an ultra endurance athlete and typically run 5 – 6 days per week. In addition, I also do core and body weight exercises.

    As a new keto adapted runner, I was wondering if you could share advice on what to eat both pre-workout and during workouts. I’m a little confused on when I should run with no pre-workout meal and when I should consume calories during a workout.

    If I understand correctly, it looks like you would recommend something similar to this protocol for a long run ….
    “About 90 minutes prior to the ride I consumed 4 eggs fluffed with heavy cream, cream cheese, coffee with heavy cream, and my usual 40 mL of MCT oil.”
    During workout consume ….. single serve cream cheese, UCAN & nuts.

    How about for intervals/track repeats? Utilize the protocol that you used for your swimming intervals?
    “During this workout I consumed nothing and prior to the workout I consumed my usual 40 mL of MCT oil.”

    How about tempo runs?

    What is the optimal strategy on using BCAA’s? Do you recommend using UCAN pre-workout for high intensity runs (e.g., intervals, tempo) or just during long runs?. Thanks in advance for taking the time to answer my questions.


    • Dean, too complicated for quick response. I do most of my workouts fasted and only consume BioSteel’s BCAA (HPSD) in-workout, since I do nothing over 3 hours these days.

  • Tom A

    Dr. Attia, thank you for the work you have done. I have been experimenting with myself pre and post workouts. I have been following a strict carbohydrate reduction (less than 50 grams a day) paleo lifestyle for a while now. When testing my blood glucose (for fun) before high intensity (kettlebell swings, push ups, overhead lunges, burpees etc) short duration workouts following a fasted state of 16-17 hrs my blood glucose will range 75-85 mg/dL. Post workout my blood glucose has spiked to 150-168 mg/dl. What are your thoughts? My first question is does that seem “normal”. My other questions is: will consuming food (hefty serving of mixed green, avocado, green/kalamata olives, lots of EVOO, few table spoons of heavy cream, protein under 35 grams etc. ) 10-15 minutes post workout with an elevated blood glucose level have negative effects on a ketoic state?

    • Discussed in this post or previous…hepatic glucose output.

  • Cooper

    First off, I find myself returning to this post often because of the evaluation of the data. I’d like to see more like this.

    Second, I stumbled across this article.
    which states “For example, when your body burns fat or carbohydrates to fuel muscles, one of the byproducts is H2O.” combined with your description of Krebs Cycle in a previous post, makes me wonder; have you experienced, or seen any impacts, on dehydration now that you are in Ketosis?

    • I’ve always been pretty resistant to dehydration, relative to a “normal” person, so I have not really noticed a change one way or the other. I’ve heard theoretical arguments, but seen no data.

  • Tom

    Hey Peter,

    I am wondering if it is possible that hepatic glucose output can hinder one’s ability to get into, or stay in nutritional ketosis? Are HGO and Ketosis fighting one another?

    I have been eating very low carb/high fat for about a year. Early on I had no trouble getting into and staying in nutritional ketosis, but lately it seems that even with very low carb intake I cannot seem to get there. One of the things that I did notice is that my morning glucose numbers were higher than the prior night before I went to bed. I have also been less physically active lately, and I am sure that has something to do with it as well.

    Thank you for all of the great work that you do

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  • Sean

    Dr. Attia,

    Apologies for resurrecting this post from years ago! I’ve used ketogenic diets in the past with good success, but this is the first time I’m doing it in conjunction with serious training. I’m on about 3.5 weeks now, down 13lbs, and producing solid ketones according to the dipsticks. All good, right? I can’t train like I used to. As soon as I start running or cycling, my legs start burning as if they were filled with lactic acid. My run pace is now several minutes per mile longer than it used to be, and my heart rate is absolutely pegged, regardless of pace/effort. Spent an 8 mile run yesterday at an average 178bpm, and slower than molasses.

    To me, it feels like my body just can’t access adequate energy on demand during exercise, but I feel fine any other time. Any thoughts? Thanks for your input.


    • Under extreme exertion it takes much longer than 3 or 4 weeks to adapt. Took me 12 weeks for first big improvement, then about 18 months to exceed where I was at outset for top-end anaerobic power.

  • Jon

    Just read this article:

    This should be an interesting journey!

  • Ann

    Dr. Attia:

    I am trying to get a base line on all of this information. Is it appropriate to say a 58 year old woman who would like to lose weight and maintain a workout that involves weight lifting and aerobic style exercise (five-six times a week for 30 minutes) could do a low to very low carb diet without fear of ketosis problems? I am a healthy “normal” female who is extremely efficient when it comes to storing and keeping my stored fat :(. I would like to say my metaboism is sluggish but I don’t know that for sure. I have no health issues. Any insight on this would greatly be appreciated.

  • Matt Davis

    Hey, great website you have here man.

    I’m an athlete that comeptes in brazilian jiu jitsu, and currently am doing rock climbing about 5 times a week, and I am on a consistant 30 grams of carbs a day. I always have great energy (although I do take MP Assault prior to exercise, which has a few grams of carbs and other things).

    what I wanted to ask (and maybe recommend) to you is something called “miracle berry”. It’s a berry that has a specific protein that attaches itself to your tongue’s sweet receptors, and activates them when an acid makes contact. So basically, you chew and such on the berry for about 60 seconds, and for the next 1-2 hours, anything sour you eat tastes sweet.

    I have been drinking pure lemon juice + water that tastes like a very sweet lemonade. I also make LOADS of drinks with lemon in them that taste completely like desserts.

    I’m soon to be trying making an icecream with lots of lemon juice, which should also taste like 100% sweet icecream.

    I’m surprised more lchf/keto sites don’t talk about this berry? Have you heard of it? And if you have, why is it not more talked about?

    Here’s a wiki on the fruit in question:

    P.S. I know lemon juice has some carbs, but it’s low enough that I can accomodate it into my diet without falling off keto (I’ll just cut back on some other source for the day I eat the berry).

  • Santiago

    Peter, I’m passionate about nutrition and exercise, and I really like to understand the science behind everything, and your blog is in-depth and didactic, you’re doing an awesome job here.

    I started keto a while ago, and I’m taking some green tea extract to help with the fat burn, along with albuterol.
    I now know that catecholamines, which the extract has a lot of, stimulate glycogen release through the liver.

    Do you think I”m doing more harm than good by taking the extract? I’m using ketostix to get a rough estimate of where I’m at (I”ve found the metallic taste in my mouth to be a better indicator of ketosis, though), and all of the markers seem normal, so I”m still ketotic, but I’m looking to optimise fat mobilisation.

    Thanks for your time! Also, what’s your opinion on sugar alcohols?

    • Santiago

      Nevermind, I read the bottle again and it’s high in CATECHINS, made me wonder why green tea would have epinephrine, haha.

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  • Adrian Wainwright

    Hey Peter, I’m also going to raise a year-old post, but this is also my first time reading it.

    Apologies in advance for all the detail. The crux of my question is the impact of exercise and keto-adaptation, especially in the early stages, and especially relating to heart rate.

    I am five weeks in. Started at 80kg and am down to 74kg – target is 68kg (which would be 5% body fat). My fasting glucose mean is about 85 (testing at home) and fasting ketones have been up to 1.0-1.5 on average (for past week). Carbs are 20-25g per day, mostly foundation veggies. And eating about 100/120g protein, and 100-140g fat. No cheating so far with food, altho I have had two IPA’s in those five weeks …

    I did get a few “flu” symptoms that I am countering with 2000mg of sodium (stock cube) in addition to salt in food, and two 99mg potassium tablets, as well Primal vitamins and drinking 40-60oz water. “Flu” has largely cleared up. The one thing that’s persisting is a weirdly high heart rate.

    As context, when in good cycling shape (I’m a Leadville 100/Cape Epic rider), I have a resting HR of about 50, and a field-tested LT HR of 162 at 320W at about 74kg. As of a week prior to the shifting to Atkins induction, my LT power had dropped to 290W with LT HR @ 165bpm at 80kg, and resting HR of 54. I don’t ride anywhere near as much these days as a relatively-new parent.

    As of yesterday morning, my resting HR was 75-80bpm – and I can really feel it, and it woke me up Sunday night. When riding on my spin bike at 220W average, I am up at 165bpm – again, I can really feel it. The same was true on a 50km tempo ride this weekend – av HR of 169 @ 214W (but RPE was probably a 7 at the most). That compares to 155bpm @ 203W for the same ride two weeks ago.

    I drank about 80oz of water yesterday and it seemed to help my HR and brought it down for a while, so I am wondering if this is simply a case of not enough fluid, or whether its related to minerals?

    Have you ever had ketosis kick your resting and exercise HR so noticeably up like this?

    • Yuri

      Hi Peter,
      Just to add to Adrian’s comment above. Mine was a similar story (albeit with less impressive wattage). Now I’ve been in ketosis for over 10 months and although the “during the exercise” HR numbers have come down to their historical levels – my resting HR is still about 15bpm above what it used to be prior to getting started on the ketogenic diet.
      Thanks for your time!

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  • Marina

    Dear Peter,

    Thank you for such an amazing website.

    My mum has always been overweight even when she was in an almost starved state (living on water and some rice). Now I have a lot of trouble convincing her that her foods are too high in carbs (many Korean foods are low in fat, protein and high in simple carbs such as potatoes, flour, rice etc).

    Recently she’s been having a lot of issues such as high cholesterol levels, knee problems due to her weight but she thinks they are the result of consuming too much red meat. On an average week she consumes probably one small portion of red meat or none so I honestly do NOT for a second believe that red meat is causing her any problems. Her low-fat high fructose yogurt, fruit juices, sugary muesli bars, wheat biscuits are behind all of this.

    It can be very frustrating to see someone you love follow such terrible guidelines learnt in their childhood (at school) and risk their health but I am making slow progress all thanks to your highly detailed blog. My parents still think I’m a little crazy but they are slowly making changes.

    I just wanted to thank you since I’ve been following your blog for a year now and have never left you a comment. Just knowing that someone actually puts their time and money into sharing critical information (all nicely laid-out) for others for free is an inspiration in itself.

    Thanks again!

    • Thank you, Marina. Very kind of you to say this.

  • kyle knotek

    Hi Peter,

    I’m a giant fan of your personally and professionally. You’re definitely a pioneer in the field and someone I look up to. You’re one of the big reasons I got into ketosis in the first place. I’ve studied a lot of your work and also some of Phinney’s work. I am currently a professional soccer player nearing the end of my prime and have started experimenting with ketosis to see if it can take me to another level physically during my matches.

    I have heard you speak of insulin being the driving factor of ketosis, but it is a popular belief that lack of liver glycogen is the driver of ketosis. And here, you say that your higher glucose levels are a result of emptying of liver glycogen (therefore, confirming the former of the two above theories of insulin and not liver glycogen being the determinant factor). My question is how do we know this glucose increase isn’t a result of muscle/internal catabolism to achieve this higher glucose level instead of hepatic glucose.

    Would love to hear back from you. Thanks again for trail-blazing my friend.

    Kyle K.

    • Kyle, I think both play a role, actually. Even in complete starvation (or hypocaloric KD), the body’s stores of glycogen remain about 50% full (largely due to GNG from glycerol in the case of starvation, and probably a combo of this and protein in the case of KD).
      I favor the HGO argument for the simple reason, that even in starvation, if you administer glucagon to a person, glucose levels rise (implying the glucose is coming from the liver).

  • kyle knotek

    Great. Thank you so much Dr. Attia,

    I know Volek/Phinney have proved that muscle glycogen stays around 50% full, but I haven’t seen anything conclusive around hepatic glycogen levels. I have been doing a little experimenting on myself lately through my training. I also think about the reasoning of our evolutionary mechanisms when looking to answer these questions with no conclusive answer our there. I just can’t rap my head around the idea that the liver would burn fats if it still had some glycogen. I do think lactate and the Cori cycle can definitely play a role in higher blood sugar levels during exercise. I do see what you are saying about glucagon, but wouldn’t the body be able to produce glucose from degradation of muscle and GNG from the resulting amino acids to accommodate to glucagon? So the same mechanism our body would use if on a HCLF after glycogen had been depleted.. I’d rather this wasn’t the case, but just trying to wrap my head around it.

    • Tough to justify liver biopsies, but the glucagon experiments imply hepatic glucose output (since muscles can’t release glycogen into general circulation).

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  • Chris Hall


    I have been diagnosed with Metabolic syndrome and have gone on 1000MG Metformin, and a ultra low carb diet. My Triglycerides are close to 700 and my diet is fairly clean. Obviously, this is genetic as I cannot loose a pound even if I ride 120 Miles a week. Interesting write up on athletic performance in ketosis. I always assumed you had to consume carbs to have enough energy for duration training. What your saying is your liver has the ability and store to convert glucose while maintaining ketosis and you don’t give up much in the way of energy stores.


    What supplements should one be on if you are endurance training in nutritional ketosis?

    Does your body need less endurance training to loose weight in ketosis?

    • I don’t know the answer to your question. It probably varies by person, though.

  • Mark

    Dr. Attia,

    I’ve scanned back thru several posts looking for a reference to a BG point which stops fat burning and if there is one I have missed finding it and apologize. I was told a fat burner would bonk cycling or running if their BG got over 100 mg/dL. This was later amended to be 100-120 mg/dL (crossover zone). Is this in fact true, to your knowledge? I was told fat burning quit and I was only burning glucose. Being a person in dietary ketosis (~30 grams of carbs per day, never more than 40 ever in the last 2 years) I don’t believe this and believe that this information was written not with the possibility that a ketogenic diet being used at all times even while training for a sport. I feel like with most other studies, People on long term true LCHF diets are not included in the performance studies.

    I feel this is probably more complex than just a simple YMMV where a person crosses over, but can you let me know if my informer is wrong or right and maybe point me to a source of further reading.

    Thanks for the blogs, looking forward to more, especially the ICU one I didn’t run across yet.

    • Not sure it’s that “simple.” That’s only one part of it. Look at the fat flux post or a detailed explanation of lipolysis.

  • Jerry Salazar

    First off, thank you for all the information you provide. I’m a Type-2 Diabetic and have struggled with weight and have now read and implemented this low-carb way of life, which is really showing progress. I take Lantus, metformin, and meal time Humalog, if necessary. I really enjoy high intensity cross-training, however it does elevate my glucose considerably. Over the long haul is this going result in the inability to be in ketosis through out the day or am I not understanding the HGO concept? I don’t want to be injecting unnecessary insulin through out the day and overall I’m trying to eat my way off my meds if that makes sense. Again, thank you for your time and information. By the way, I live in the Rio Grande Valley and we really need some resources for the Diabetes and Obesity epidemic down here!!!

  • Yaron Hadad

    Great post!

    Do you think it is possible to get into a state of ketosis on a plant-based diet? It seems like consuming <50g/day of carbs on a vegan diet without mostly relying on commercial products (and tofu) will be significantly harder… (one cup of any random legume typically has 40+ grams of carbs, and without legumes it's pretty hard to get enough protein and iron). What are your thoughts about this? If you know any good sources, I'd greatly appreciate them.

    • Yes, but probably high in N-6 and relatively low calorie.

  • Samantha Long

    Dr. Attia:

    Many thanks for your fantastic blog, and for your sacrifice of time to maintain it!

    I wish I could post pictures so you could appreciate my pre-keto/pre-Attia-blog-reading self with the current incarnation.

    July 2013, at age 46: female, PCOS, metabolic syndrome, Hashimoto’s, chronic anemia due to multiple fibroids the size of boulders, height 5’7″, weight 230. Exceptional diet by conventional standards: 80% organic, no fried foods, no processed foods, no “cheap carbs, no meat of any kind excepting fatty fishes like wild sardines, wild salmon, wild halibut, and longline-caught albacore, omega-3 eggs, quinoa, steel-cut oats, brown rice, barley, faro, etc., and the spectrum of vegetables and fruits.

    Began reading your blog, became inspired, and found a doctor who would give me iron infusions so I could find enough energy to get motivated, and moving, and then found a trainer and joined a gym. Two years later, July 2015: metabolic syndrome completely reversed. Hb1ac 5.1, glucose levels consistently in the mid 80s. I occasionally eat beef, pork, duck, lamb, etc., but try to stick to my fishes and occasional shellfish, and get my fats from avocado, evoo, coconut oil, eggs, and nuts. I attempt to keep my carbs <50g by eating zero grains and virtually zero fruit, and sprinkle in leafy greens and vegetables wherever possible, although I have to cook most vegetables to reduce goitrogenic effects. Weight 150. Gym 6-7 days per week, mostly strength training with HIIT and bootcamp workouts 3 times per week. Still rolling despite Jan 2014 ovarian cancer diagnosis following surgery to remove 12.5cm mass covering right ovary; diagnosis was incorrect—corrected to widespread endometriosis//mass was endometrioma. Also still rolling despite Feb 2014 melanoma diagnosis and subsequent wide excision surgery.

    No current meds except iron infusions. Here's my current concern: I took a peek online at my blood work performed prior to a recent iron infusion, and was surprised to note that my creatinine was 1.2 and corresponding GFR was 48, BUN = 25. I began drinking lots of water, and had them re-check. On the re-test, I had them fax my results, and GFR (89) and creatinine (.70) had straightened out, but my BUN was 22 and my BUN/Creatinine Ratio was 31.4, so the brunt of whatever imbalance I am experiencing had obviously shifted from my kidneys to my liver. I freaked out a bit, and had the establishment fax over my labs from visits in March, May, and the two recent (July), and compared all four, and it appears some/all of these numbers have been in the red from time to time over the course of these last few months, with no comment from the doc/nurse/lab. It appears they only run the test to use my LOW iron/ferritin levels as argument so my insurance company will pay for the $5000 infusion, and pay no notice to the other numbers?

    Question: is it possible that my keto diet could have put me here? Or is iron more likely to blame? Too much protein? Or simply a factor of massive monthly blood loss from my cycle? Is a nephrologist my next move?

    I am doing so well and feeling so good, and am so disappointed and worried that I may have damaged vital organs, all under the nose of physicians??

    Do you accept patients from Memphis, TN? 🙂

    Many thanks in advance for any response anyone might have, and have more numbers I can post if additional detail will assist—-


  • Bill Wightman

    Just want to thank you for all of your honest experiments and reporting. At 56 years old I started a keto food program 14 days ago and passed .5 mmol/L after 5 days and have risen to ~2.2 depending on the time of day/exercise. What is fascinating is that I came home from a group ride last weekend feeling good with my glucose at 61 mg/dL while at the same time ketones were 2.6. I would normally be sitting on the curb at that glucose level. Also experimented with a big Thai meal with white rice and went from 2.2 morning to .4 morning to test my ability to cheat. Another thing, just that one meal changed the whole character of my sleep (as suggested by a sleep app graph) from deep almost motionless sleep to a modestly fitful but deep sleep. If I go back 12-14 days on the app graphs this fitful pattern shows up again. I think it is possible that keto eating might improve circadian adjustment, I now have a hard time staying up late and I wake up an hour earlier on average. Still pushing out the no carbs (road) cycling endurance. Probably take another four weeks to be full power plus at the end of a long ride. Thanks. Good stuff.

    • This kind of tweaking and physiological self-experimentation is why I spent nearly 3 years in ketosis. Just so cool to see what happens at the boundaries.

  • Tom Pietrzak


    When using MCTs would you recommend coconut oil or a specific MCT oil. Also would taking MCTs bring you out of ketosis since it does not illicit an insulin response.


  • Ed

    Hi Peter,
    I must say i am enjoying the huge amount of information on your site – even though a lot of it is totally over my head! Anyway i am experimenting with a ketogenic diet in the hope of completing a long distance ironman triathlon in June. The thought of avoiding all the gastric upset that i have suffered in previous races is most appealing but i am confused as to what i should consume during the race – now obviously the aim is to stay in fat burning mode for the duration of the race but is there a limit to how much race carbs one should eat. Looking at other endurance athletes who follow a ketogenic diet e.g Pete Jacobs and an ultra runner whose name escapes me both seem to consume huge amounts of carbs during race – which must take them out of ketosis yet it does not seem to affect them adversely? Or would you advise me to simply stick to UCAN super starch (despite the disgusting chalky taste) and fat from say nuts and even 85%cocoa chocolate? Have you any advice or guidance and are you still in ketosis?
    With thanks Ed

  • Zidan

    So wait, just to make things really simple:

    Can the athletic advantages of being in ketosis AND being on a high carbohydrate diet be achieved, simultaneously, if one is on a high carb diet, whilst also taking a ketone supplement? The one I’m referring to is KetoCaNa (or KetoForce).

    PS: Thank you so much for your posts. They’ve actually helped me study a lot more for my Biology assessments without me even realizing it (got my first A star 3 weeks ago!).

  • Cobus

    Hi Peter,
    I’m SO glad I came across your blog. I’ve been on a LCHF lifestyle for about 4 months now and I’ve lost 11.5kg with more to come. I am so happy with my life and in the best shape of my life at 43. I do a daily (fasting) 12-minute HIIT workout first thing in the morning 5 days per week and I was very concerned about muscle loss when I read about ‘cannibalizing your muscles’ on other blogs that push the HCLF lifestyle and all kinds of strange ‘carb-loading’ permutations being required to not lose muscle when you are in ketosis. If I understand you correctly, one can still build muscle and lose fat while on LCHF? I do seem to have lost some bulk, but my sense is that it’s probable adipose tissue in the muscle which is being used when I am in ketosis, so I just need to carry on with my existing regime.

    Thanks so much for a brilliant blog- you have won a fan for life! Strength to you.

    • In general, without anabolic agents, it’s tough to gain muscle and lose fat simultaneously. They tend to move together. But it can be done…requires very careful nutrition and training (and good genes).

  • Matt

    Peter I love the enthusiasm but you can’t do sincere science with a sample size of one or draw any meaningful conclusions…

    • dingleburry

      which why he has repeatedly, explicitly stated as much. Thanks though.

  • Andrew

    Hi Peter. Thanks so much for your blog and all the information it contains. I’ll also have to thank Tim Ferris for introducing you on his podcast.
    Sorry to bother you with a question, but I really can’t think of who else to ask. I’m 55, fit and healthy. I also have two parents with Alzheimer’s disease. I’ve recently begun a ketogenic diet and I’m going to try to get a script for Metformin (not because of any metabolic indicators). Can you think of any reason why this would be a bad or terrible idea?

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  • Tom

    I came back to your blog after reading about this guy who apparently clears lactate by having a “high alkaline” diet. What are your thoughts? Google “Dean Karnazes”. Multiple articles state that they did a lactate threshold test, and had to give up after more than an hour, because he didn’t accumulate lactate.

    • Nothing to do with alkalinity of diet. It has to do with lactate transporters on cells.

  • Roman

    Im not too active (22 year old male.)..I walk alot nothing crazy. I eat about a bundle of kale which is the extent of my carbs. I do eat about 100 grams of protein through organ meats (cheaper). Will this really effect my ketone levels if i eat a good amount of saturated fat? Also does it matter if i consume that protein all at once? Will that effect if my chooses to burn the amino acids over the fatty acids? or does that happen simultaneously? I made sure to look at all the comments before so i dont ask a repeated question. Thanks Dr.

  • Robert A


    Thank you for taking the time to make the information you provide understandable to us non-medical lay persons! I am able to understand and apply the information you present in a way that hundreds of hours reading medical report findings have never produced. I liken it to trying to learn algebra without knowing arithmetic.

    On to a more specific question… I recently completed a 5-day water fast with a full metabolic / blood / urine round of testing and a couple of the results surprised me and I am hoping you can provide some insight into the results in light of water fasting for 5-days?

    Component Your Value Standard Range Flag
    Proinsulin 34.0 1.5-14.9 uIU/mL H
    Insulin, Free 14.5 1.5-14.9 uIU/mL
    Albumin 4.8 3.2-4.7 g/dL H
    Total Bilirubin 1.2 0-1.1 mg/dL H

    Total cholesterol 177 0-200 mg/dL
    Triglyceride 237 0-150 mg/dL H
    HDL cholesterol 28 mg/dL L
    LDL Calculated 102 0-100 mg/dL H
    Cholesterol to HDL Ratio 6.3 0-4.98 H
    LDL:HDL Ratio 3.64 1.00-3.50 H
    VLDL (Calculated) 47 4-30 mg/dL H


    Robert A.

  • PAUL

    I have been in ketosis for 2 months and have a few questions, I struggle to get into / maintain the +1.5 optimal zone. [I’m generally eating 30-40g carbs, 70-100g protein]
    1. Does your body improve over time, ie if I keep doing what I’m doing can I expect my ketone score to go up?
    2. It seems I’m sensitive to the amount of protein I consume. It looks like I need to keep below 85g maybe less. (I’m 57Kg 10% body fat so that puts the protein level right at the lower end). I weight train with heavy weights, trying to build mass (which I find hard) I worry re having such low protein. Should I, or do you require less protein when in ketosis?.
    3. What type exercise (HIT training, heavy weight training, low level endurance, high level endurance etc.) is best for increasing the my ketone level score to help get me in / stay in the optimal zone
    Any answers greatly appreciated

  • Jessica

    Is there anyway that your decrease in ketones during the high intensity exercise could be due to you using the ketones for energy?

  • Mike

    Hi Peter,

    Not sure if you are still monitoring this but just in case…

    Just looking at the charts it appears that there is a reduction in lactate with an increase in ketone metabolization.

    I came here via a google search looking for this information because last Friday I had an unusual experience in my swim workout. I usually start off with 4-500 yard warmup and in that initial swim I almost always go through a lactate cycle in my upper arms between 200 and 300 yards.

    On Friday I did two 500s followed by 10 5 100 IMs followed by another 500 and never hit a lactate cycle. I had been consuming 2-3 tablespoons of mtc oil per day for the last week. Earlier in the week I did two 1-1.5 mile lake swims while camping. I always look forward with some trepidation to the discomfort of the lactate interruption and was very surprised to not encounter it. In addition I have an snp that suggests that I will not have success trying to extend the lactate cycle.

    So my question is can mtc/ketosis help to avoid lactate/lactic acidosis. This was a one time sample but it was as I said very surprising.

    I’m 72 diagnosed T2D then changed to delayed onset hyperglycemia. My last 3 a1cs were 5.5 5.5 5.4 and my fasting is usually about 108. No meds other than supplements though I am considering metformin and perhaps a fibrate for LDL due to rs1800206 though the evidence for coronary risk doesn’t appear that high and an angiogram earlier this year showed 20% and 30% blockages.stenoses with minimal lumen damage which I think at 72 is not bad.


  • Geno

    Hey man, thank you for all of this. I’ve been back and forth searching like crazy for some legitimate source of info on this subject and your posts here are beyond what I thought I would find.

    Question: I box and do jiu jitsu 3 days a week (Tues, Thurs, Sat). Because of my schedule and the gym’s schedule I do a full afternoon of training on those days (3 to 4 hours each day). It’s pretty intense, live sparring things like that. My first question is, in your opinion, what is the most optimal diet for this type of training (Keto, low-carb, or carb-loading)? If just low-carb, how many grams of carbs roughly? I hear a lot of 100-150g but i understand that degrades my fat-burning efficiency. I’d rather be fully Keto if possible.

    My second question: I come from a high-carb/low-fat upbringing. I’ve studied diet most of my life. I truly believe in everything you’ve written here. But since I don’t eat dairy I really have few fat options I feel. Basically all I can gather for fat intake is from Eggs, Beef, Avocados, Olive Oil, Coconut Oil, and Nuts. Once I lay out the math with a 2500-3000 cal diet at even, say 1g of protein per bodyweight which may be on the high side, only 50g of carbs, that leaves a heck of a lot of calories to meet my daily requirement. So my question is, should I truly be eating that much fat? Also since carb intake is next to nothing, and most good fats are either part of my protein sources or from oils, I feel like the physical meal sizes would be such small portions of food and lots of oils which are simply liquids.

    I don’t mean that to sound like a challenge to your obvious expertise on the subject, quite the opposite. I’m simply trying to wrap my head around it. The science is very logical. But considering the quantity of food I’d eat on a predominantly carb diet, I’m having trouble actually taking that science and implementing it into daily meals. I apologize for the length. And again I appreciate your site I can’t say it enough! Thank you

  • Adam Imiolek

    I am interested in what you think is the best adaptation for high lactate demand events? Both the 200 IM swim and the 800m run are about two-minute events. You comment that your ketosis adaption took around 12 weeks. Can you estimate your performance on a SAD diet vs. a ketosis diet? Are there any studies in humans comparing sugar to fat fuel?

    • Hard to see keto offering an advantage for ~2 min events.

  • ben

    Can you suggest any high-intensity strength training exercises that maximizes 2b fibers in us 40+ old folgies?

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  • Brian

    Peter – Thank you for your excellent post and self-experimentation! Your experience with the fluctuations in glucose and ketones match my own, and your explanations match a lot of what I’ve read. Your explanations and honest interpretations are outstanding. The reason I came back to your post is because I was diagnosed as Type 1 diabetic a few months ago, and what you’d call the ketogenic diet makes it much easier to manage (i.e. small inputs of carbohydrate mean smaller doses (and thus mistakes) with insulin). I’ve been able to perfect my management except in one realm: high intensity exercise. I noticed that your glucose went up to 132 when you were lifting weights, but of course, during this test you ate some stuff. There aren’t many non-diabetics measuring their blood sugars – and even fewer who are also athletes, so I’m curious: how high can your blood glucose go from intense exercise? Well over 130? It’s been a long time since you’ve done this post, so I assume you’ve gathered more data. Mine can increase from 85 to 190 in 6 minutes of high intensity – with no food. My definition of high intensity would be trying to run a sub 5 minute mile, so a big muscle group and no resting like you get in weight lifting. If you think about that, it’s an amazingly rapid “dump” from the liver into the bloodstream. My curiosity is: does a healthy person also experience this same hyperglycemia? Everything I read says if you go over 130, you’re diabetic… I’m curious about this because I am trying to optimize my performance for 5 minute events. If the blood glucose is shooting upwards, it seems that it would be beneficial to have more insulin on board so that the liver’s dump could be utilized instead of “wasted.” Furthermore, having high blood sugar could potentially decrease performance as well. Injecting insulin before a workout is scary, though, because you could potentially have dangerous hypoglycemia. I’ve been using a Dexcom G5 CGM to try and maintain glucose at 85. It’s very helpful, but unfortunately runs about 20 minutes behind a fingerstick.

  • Dreif

    First, let me say how much i appreciate the knowledge you provide. Your articles are undoubtedly some of the best as far as nutrition goes. Giving out free information like you do is really helpful. Anyway, lets get to the topic.
    Im a 17 yrs old basketball player who dreams to play pro!! But for that to happen i have to work a lot!! So, i wanted your help with my diet. Im training a lot, at least 2 hours every day and some times i train twice a day. I love eating one low carb meal a day (at night) . I primarily eat a huge bowl of salad (tons of veggies, some eggs and cheese) and some animal protein (meat/fish). Here are my questions: 1) Will this type of diet be ok for me? Have in mind that i still want to grow as much as possible but i want to lean out too!! 2) Will i be able to recover from my workouts?? 3) Are carbs a must for such a level of high intensity training?? Let me say that i love training fasted since im full of energy and that i dont have any issue eating a huge meal at night! 4) Since its hard and pretty expensive to find high quality grass fed meat everyday, would it be ok to eat casual meat?? Finally, 5) what kind of diet would you recommend to support my needs?? Looking forward to your answer.
    Kind regards,

  • Jaap

    Hi Peter,

    I practice breath hold diving several times per week and have recently started researching how muscles perform under hypoxic conditions. I have posted several articles on this on

    One thing that I am very interested in is the potential advantage of a lower RQ during freedives. A lower CO2 production implies a lower urge to breathe for freedivers, that part of the story appears simple. I wonder whether a lower oxygen demand for a given power output would benefit freedivers? Your experience with cycling at altitude (unacclimatised) sounds encouraging. During freedives, oxygen saturation is perhaps initially increased by the higher partial pressure of oxygen at depth (2 – 4 atm), but then gradually lowers as oxygen is used and vasoconstriction limits the blood supply to the limbs. Many divers experience muscle fatigue or even failure at the end of their dives, which is commonly interpreted as the result of ischemia (and anaerobic glycolysis). I wonder whether we can prolong the aerobic part of our dives in nutritional ketosis.

    One caveat is that freedivers do their best to limit their energy expenditure under water, and you have stated elsewhere that the basal metabolic rate in nutritional ketosis increases.

    I’d love to hear your thoughts on this,

  • James

    I know this is an old topic for most but it is new for me….

    In ketosis, my RQ at 60% max VO2 is 0.77 (at last check), telling me I am getting only 22% of my energy from glucose and the remaining 78% from fat. So, how long do my depleted glycogen stores last? Nearly 5 hours. Why? Because I barely access glucose at the SAME level of oxygen consumption and the same power output.
    End Quote.

    I tend to look at these items or this subject through an evolutionary set of of glasses. The above make a lot of sense as we were far more active during the hunter-gather portion of our species existence on this planet. We would have needed a mechanism to stretch our energy reserves during the hunter-gathering portion of our day. This, to me, is that mechanism. This is all driven by our specific active set of genes as well through the several million old library of knowledge we all carry inside each and every cell that we call DNA.

  • arnold

    Hi Peter,
    I’ve been having an issue with insulin resistance, sort of a prediabetic diet heavy in coke and chips, although i’m not fat. Recently have got into a ketogenic diet as the best way to reverse my condition. My question to you is: Should i include sprints and weight training in my training regimen considering the studies that say they improve insulin sensivity (although i know i wouldn’t be in a peak performance state) or just stick to aerobic exercise?
    Keep up the good work!

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  • Mary

    Let’s say a person is fat adapted and they are an endurance athlete- so for running, they can sustain a HR of around 145-150 for hours. For a trail marathon lasting 3ish hours, 200 calories of energy chews are eaten. Now, lets say this person needs/wants to transition to cycling where short efforts at high intensity will occur. How does one transition from eating minimal carbs (a high fat diet) to one that has more carbs in it without totally blowing up- physically and performance wise.

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  • Bob

    Hi Peter! I have seen similar results with regards to high intensity training while in ketosis/fasted state, i.e., “Sprint8” style, or 5-6 rounds of alternating 30 seconds moderate sprints (~80% max HR) followed by 30 seconds recovery on an exercise bike.

    My ketone levels dropped significantly 1 hour post workout, and my glucose spiked. But when I repeated the experiment but added ~21g of a sports gel 30 minutes prior to doing the workout, it spiked my glucose prior but it prevented my body from dumping glycogen from my liver during exercise, and my glucose levels were back down to baseline levels 1 hour post exercise. However, it kicked me out of ketosis.

    Interesting stuff!

  • Unlikely given the rapid time course (minutes).


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