August 26, 2013


Ketones and Carbohydrates: Can they co-exist?

Can you "carb-load" and stay in ketosis?

Read Time 8 minutes

For reasons I’m still struggling to understand, the idea of “nutritional ketosis” (NK, to be distinguished from starvation ketosis, SK or diabetic ketoacidosis, DKA) is often discussed and debated in much the same way as religion or politics. Perhaps this can be said of all nutrition, which is a shame.  Nevertheless, in my continued defiance of such sensitive topics, I’d like to add another layer of complexity and nuance to this discussion.

The “rule of thumb” for NK is that caloric intake is determined as follows (this excludes a subset of ketogenic diets known as calorie-restricted KD which, as the name suggests, is specifically restricted in calories):

  1. Carbohydrate (total, not “net”): less than 50 gm/day, but ideally closer to 30 gm/day
  2. Protein: up to 1 to 1.5 gm/kg, but ideally below about 120 gm/day
  3. Fat: to satiety

Let me illustrate what this looks like for Joe (left), Jane (middle), and Jeff (right — an example of a calorie restricted KD), three hypothetical people in NK — but each with different caloric requirements.


As a general rule, as caloric requirement increases the proportion of calories derived from carbohydrate and protein decreases (and the contribution of dietary fat increases), even while absolute intake of carbohydrate and protein increases.

Anyone who has bought a blood ketone meter knows how tough it can be to get “into” ketosis by carbohydrate restriction (since everyone asks, I use the Abbott Precision Xtra meter which uses two different strips: one for glucose and one for beta-hydroxybutyrate, or BHB).  Most practitioners consider the minimum threshold of NK to be a fasting serum level of BHB above 0.5 mM.  I’m a bit more stringent in my practice and like to see fasting BHB levels above 1 mM.   To give you a sense of one person’s numbers (mine), over a 6-month stretch in 2013, when I was in NK, my mean (i.e., arithmetic average) morning fasting level was 1.7 mM with a median value of 1.4 mM.  The highest morning level during that period was 5.2 mM.  (The highest morning level I have ever measured in myself is 5.7 mM.)

But, it took me a long time to get it right, especially since at the outset of my foray into NK I was consuming between 4,000 and 4,400 kcal per day.  (My average daily caloric intake for weight stability was about 3,800 kcal per day, which was validated by doubly-labeled water.)  I could still easily “fall out” of NK.  For example, on my daughter’s 5th birthday she insisted I have some of her tikka masala (contains lots of sugar), naan bread, and mango ice cream.  How could I say no to a birthday girl who insisted on going to the nicest Indian restaurant in San Diego?  As to be expected, the next day my BHB was 0.2 mM, and it took me 2 days to get back above 1 mM.

Here’s a little secret I’m about to let everyone in on… I like carbohydrates. I love sushi (though I now mostly eat sashimi).  I love Indian and Thai food, though I prefer to make curry myself to keep sugar out.  I make (and eat) the best hummus this side of the Nile River. I’ve figured out how and when I can eat them to meet the following conditions:

  1. Stay in NK (except on a few occasions like my daughter’s birthday);
  2. Increase my anaerobic performance;
  3. Preserve most (but not all*) of the benefits I enjoyed when I was much more strict about my ketogenic diet.

How, you ask? By learning to calculate my glycogen deficit.

(*) For me, the leanest body composition I achieved as an adult was in strict NK with no attempts to do what I’m about to describe below.  Since I’m not a model and nobody cares if my body fat is 7% or 10%, I’m happy to be a little less lean if it gives me the flexibility to increase performance and live a slightly more sane life.  At least for now.

PLEASE NOTE: I have never suggested, and can’t imagine I ever will suggest, that a KD is “best” or “right” for everyone.  What I describe below may seem extreme, both in the amount of work required and the actual application.  I fully acknowledge that (1) this is a highly analytical approach to eating, and (2) that I’m a “freak” (my wife’s words, not mine). I certainly don’t do this often, unless a lot is on the line (e.g., a big ride), but I like having this technique in my armamentarium.

If you’ve watched my presentation from 2013 at the IHMC, then you’re familiar with RQ.  Through years of metabolic testing I have a pretty good sense of my RQ at any moment in time – when I’m sleeping, when I’m sitting around (most of the time), when I’m riding my bike at 200 watts, when I’m riding my bike at 400 watts, when I’m lifting weights, etc.  This allows me to calculate what proportion of my energy I derive from glycogen and what proportion I derive from fatty acid.  Consider the following example:

If I ride my bike at an average of 185 watts (you’ll need a power meter to infer this) for, say, 2 hours, I know my average RQ is between 0.76 and 0.80.

The approximate formula is %CHO = 3.333*RQ – 2.333, which can easily be derived from the observation that %CHO utilized increases linearly from 0% at RQ 0.7 to 100% at RQ 1.0.

Furthermore, I know my VO2 at 185 watts is 2.9 liters per min, which means (using the Weir formula which I presented previously) my energy requirement was about 14 kcal per minute, or 1,680 kcal over 2 hours.  Hence, of these 1,680 kcal needed to pedal 185 watts for 120 minutes, 336 to 554 kcal came from glycogen.  In other words, I utilized between 84 and 138 gm of glycogen.

(By comparison, several years prior to being in NK, this effort in me would have taken place at a slightly higher VO2 – closer to 3.2 liters per min – and at a much higher RQ – between 0.90 and 0.95 – meaning the exact same work output would have required somewhere between 300 and 400 gm of glycogen!  That’s a real state of metabolic inflexibility.  Basically, I was entirely dependent on carbohydrates for energy.)

Since the first metabolic priority for ingested carbohydrate is glycogen replenishment, I can, in this setting, consume probably somewhere between 60 and 120 gm of carbohydrate following this ride and stay in ketosis.  Why? Because those carbohydrates are prioritized to replenish my glycogen stores AND I am highly insulin sensitive.  Note the *AND* in this last sentence. (The especially astute reader will realize some of this glycogen debt will be replenished by protein and glycerol, the latter of which is liberated by lipolysis – see post on fat flux for a primer).

Clearly I didn’t consume this amount of carbohydrate on my daughter’s birthday, so why was I out of ketosis the next day? Because my glycogen debt was not high.  Of course, I knew this and didn’t really care.  But, if I know my wife wants to go out for sushi one night, and I know she’s going to make me eat a California roll, I can “rig it” such that I show up to dinner with a glycogen debt appropriate enough to enjoy them without significantly interfering with my liver’s BHB production.

Extreme example

At one point, I did two tough bike rides on consecutive days.  Each day we rode 110 miles under challenging conditions.  Over 6,000 feet of climbing each day and very strong winds, which were either headwinds or cross-winds.  On top of this, we rode pretty fast. For the purpose of illustration I recorded everything I did and ate on the second day, which I rode a bit easier than the first day.

The second ride took 6 hours and 5 minutes.  My average normalized power output was 225 watts, and arithmetic average power output was 184 watts.  Based on mechanical work output, this required about 5,000 kcal.  Factoring in the other 18 hours of that day, my total energy expenditure was about 6,800 kcal for the day, obviously not an average day. (A detailed explanation of where the extra 1,800 kcal were expended is beyond what I want to get into now, but it’s basically the energy required to keep me alive – transport ions, contract voluntary and involuntary muscles, etc. — plus move me around, and digest food).

So what did I eat that day?

  1. Breakfast (pre-ride): 5 scrambled eggs, 2 sausage links, 3 pieces of bacon, coffee with cream.
  2. In ride nutrition (I spread this out over 6 hours): 14 oz (not a typo) of salted cashews, 2 Quest bars, 1 peach, 1 apple, 6 bottles of Biosteel High Performance Sports Drink, water. (Since I know someone will ask, I did not consume super starch this day since I was craving cashews as my carbohydrate source and was craving more sodium, given the 90+ degree temperature.)
  3. Late lunch/early dinner (post-ride): 2 oz ham, 3 oz pulled pork, large salad with oil and vinegar dressing, 2 slices of cheddar cheese, 6 mini hamburger patties, 2 tomatoes.

What did this amount to?

  • Fat – 351 gm, or 3,160 kcal of fat
  • Protein – 245 gm, or 980 kcal of protein
  • Carbohydrate – 321 gm, or 1,284 kcal of carbohydrate

(I used package information and Nutritionist Pro software to calculate this.)

Hence, on this day I consumed about 5,400 kcal in total at the following ratio:

  • Fat – 58%
  • Protein – 18%
  • Carbohydrate – 24%

By all conventional wisdom I should not have been in ketosis the next morning, right?

The following morning, my BHB level was 2.2 mM and blood glucose was 5.1 mM.

Teaching point I can’t resist: Following 2 days of significant caloric deficit, about 3,000 kcal in total, I should have in theory lost about a pound (mostly fat, possibly some muscle) which would have been noticed on a scale.  Instead, I gained 8 pounds over those 2 days! Sure it was mostly water retention, both from the glycogen (small) and the fluid accumulating in the interstitial space (“thirds space” fluid losses, large) due to a systemic inflammatory response.  This happens under extreme conditions of exercise.  In fact, the harder I exercise, the more weight I gain, transiently.  I am at my absolute lightest following 2 days of travel (i.e., rest).  So before freaking out at the sight of the scale, keep in mind that most day-to-day weight movement in our bodies is indeed water movement into and out of the plasma and interstitial space, respectively.

What’s my point?

Context matters!  If I ate even one-quarter of that amount of carbohydrate and two-thirds of that protein on a normal day – say, 2.5 hours of riding or 1.5 hour of riding followed by 1 hour of swimming, or a day of travel with no exercise – I would have been out of ketosis for two days or more. (Of course, my appetite on those days would not have allowed me to eat 5,400 kcal without feeling sick, but I won’t get into that until a later post.) But on this day, with these glycogen demands, I was able to maintain the perks of ketosis AND glycolysis simultaneously.

There are days, though, when I overshot my glycogen need and end up with a low BHB and high fasting glucose the following morning. Conversely, there are days I underestimate my glycogen depletion and wake up with very high BHB levels and very low glucose levels (i.e., BHB levels higher than glucose levels, when both measured in mM).

Final thoughts

I felt a bit like I was in unchartered territory because the literature on nutritional ketosis hadn’t really (to my reading) explored this level of extreme activity.  In future posts, I may write about other experiences and self-experiments, including my experience with exogenous (i.e., synthetic) ketones (which I did not use on this ride, but have experimented with on other rides – no, this is not “raspberry ketones” or other such gimmicks).

2017: You can read about one of my earliest experiences with exogenous ketones in this post.

Are carbohydrates necessary to produce 225 watts or more for hours on end? Yes. But, the key is knowing how much you need and when to take them.  A lower RQ at a given level of intensity means less demand on glycogen. In my experience, working with athletes and non-athletes, most tend to make two errors (for lack of a better word):

  1. They over-estimate their carbohydrate requirement, and/or
  2. They forget that no factor influences RQ – and therefore substrate requirement – more than dietary composition during lead up to event (or “life”, which is sort of the ultimate event).

Know your engine, first.  Then fuel it appropriately.

Photo by CloudVisual on Unsplash

Disclaimer: This blog is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this blog or materials linked from this blog is at the user's own risk. The content of this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard, or delay in obtaining, medical advice for any medical condition they may have, and should seek the assistance of their health care professionals for any such conditions.


  1. >> See fat flux post.

    Thanks Peter. I had already read that, and I am not sure if the answer to what I am after is in there or not. It could be in there somewhere but some of it is over my head.

    What I have gotten from all the LCHF discussions (simplified) is that fat does not make you fat, it requires insulin to store ingested carbs and fat as fat, but it requires carbs to raise insulin while fat will not raise insulin. So my takeaway from that is that if you don’t eat carbs, but just eat fat (again, simplified), your insulin will remain low and the fat you eat won’t be stored as fat and it won’t turn into triglycerides in your bloodstream. But if this is the case, what happens to the fat you just ate (whether you are in ketosis or not)?

    I am looking for a simple explanation of this because I get asked this all the time when I say I am on a LCHF diet. They all, of course, think that fat either turns directly into fat or clogs your arteries. I tell them that fat only gets stored as fat when you also eat carbs (or something glycemic) and that it is carbs that turn into triglycerides, but I am not sure what happens to the fat that we eat when we don’t eat carbs. Does it all come out in our stool?

    • What Dr. Attia is pointing to is that you oversimplified in saying fat does not make you fat under any condition. It may not spike blood sugar and increase insulin, but it also doesn’t remove insulin entirely (which is dangerous). As long as some insulin is present in the body, fat storage is possible.

      While eating fat vs carbs, the basic difference is that you can eat an amount of fat of equal geometric area to an amount of carb (even though the calorie count is unequal) with vastly different results, meaning the calorie count is not relevant. So let’s say take 2 piles of food of equal size, one carb and one fat, the carb pile being 2500 calories and the fat pile being 4000 calories (varying per person), you will not (immediately) gain weight. But you will gain weight in either case if you eat more than that pile of either carb or fat.

      So you still have to count grams of fat, because if you eat more than that pile of fat, you will gain weight. If you overeat the fat, you will still have the advantage of controlled blood sugar, ketosis, insulin sensitivity, lower inflammation, appropriate leptin & ghrelin levels, etc., but you will gain weight as the body re-esterifies the fat it previously released from fat storage as it is not needed for energy and esterifies the new fat you’ve eaten.

      This is a simplification of what happens to most initially people under most conditions. Dr. Attia mentioned that he’s had to solve other health problems in certain patients to create fat loss, without mentioned what the problems where (elsewhere he mentioned thyroid problems), but that his first approach is always to cut down on fat consumption within a HFLC diet.

      Later on, the carb consumption will lead to much greater weight gain because of constant hunger driving up the total consumption of the carbs, sometimes to 8000 calories a day or more! Meaning that in an estimated 70% of humanity, you can’t continue eating 2500 calories of carbs a day indefinitely, because the hunger will lead you to increase calorie consumption, but you can continue eating the same 4000 calories of fat indefinitely with no desire to increase. That is the real advantage of fat over carb.

  2. Thanks so much for your invaluable contribution to health. I am a nutritional biochemist (have my own sports nutrition business) and enthusiastic competitive cyclist/triathlete who has been trying wholeheartedly a well formulated ketogenic diet, while undertaking training for an Ironman triathlon. Sadly though, 8 weeks in and my training is still suffering badly (greatly reduced power/energy) and have grown accustomed to a feeling of lactate onset at significantly lower exercise intensities. I regularly measure blood glucose, ketones, and lactate before/after exercise and have noticed trend for high lactate levels (6.0+) even when training below normal threshold pace/power. My ketone levels have only hovered around 0.5 – 0.8. I am supplementing with bullion, keeping a lid on protein and generally keeping carbs around 50-60g. The other key bit of info is that I am -and have always been extremely lean (7-8% BF) so insulin resistance likely not a problem (although father has type II diabetes + metabolic syndrome). To give you an idea, my FTP is normally around 285W, I can normally easily run sub-4 min ks on up to 20K runs and I weigh 57kg with a height of 176cm. But I haven’t been able to get close to those numbers since going keto. So my reasons for taking on diet are purely performance motivated, which is why I’m starting to get disillusioned with it all as I simply can’t perform as usual on training rides with mates. Just wondering if you might be able to provide some input, particularly in the context that I am very lean. Do I need to experiment up low-gi carb intake? What metabolic situation would explain a lactate value of 6.0, a ketone value of 0.8 and blood glucose of 5.3 after an 1.5hr easy-moderate session (run-swim-run) in morning after overnight fast and consuming only water, plus a couple of tablespoons of virgin coconut oil before exercise? Can’t work out why lactate so high and feel so lousy. BTW – I love all the other benefits…less hunger, better concentrate, better sleep etc.

    • Too complex a problem for me to solve without knowing more. It takes me a while to figure these things out with clients. Could be an adaptation issue, could be many other factors.

  3. >> Re-esterification (RE) as described in that post.

    Doesn’t that just cover the part of the equation for how much dietary fat gets moved into the fat cell based on how much insulin is in your system? I don’t see where it says what happens to the dietary fat that does not go into the fat cell because insulin is not present in quantities to store it all. (Sorry if I am just being dense. But this is something that I have been trying to find the answer to for a long time. :-))

    • If there is any insulin present at all, fat will be stored. Only conditions like type 1 diabetes that suppress insulin entirely, meaning down to 0, lead to no possibility of fat storage.

  4. Simply stated: is it possible to get fatter while in NK? Can you store fat at the same time as you burn it?

  5. Peter,

    Thanks so much for the info. Your website is a fantastic resource.

    I’m having trouble finding much information that specifically addresses fueling for a 100 mile ultramarathon while in NK. I’ve been experimenting with ketosis and can comfortably do 25-mile very hilly training runs on nothing but water but I’m concerned about fueling for my upcoming hundreds this summer. Assuming one starts a hundred firmly in NK, will taking in 1-2 gels a hour during a hundred definitely kick you out on ketosis? If so, would the consequences be devastating for performance? I know that Mike Morton, for example, started Western States last year in ketosis but took in plenty of gels during the race. His experience seems to suggest that UCAN + MCT oil as fuel for very long efforts isn’t the only way to go.

    There are a lot of factors here, I know, but it would be great to hear what you think on this. Thanks!

  6. Thanks for your reply!

    I’m trying to figure out the most efficient way to carry and consume nutrition during a long ultramarathon while being in NK. This post is very useful in thinking about glycogen deficit and it got me wondering about why not simply consume gels during hundreds (albeit in a much lower quantity than someone who isn’t in NK). I love cashews but they’re not nearly as easy to carry over long distances as gels. I realize that insulin response varies from person to person, but I’m wondering if, applying your principles of glycogen deficit, gels would work just as well. And if they did kick you out of ketosis in the middle of a hundred, would there be catastrophic consequences? I know the way to find out is to try but I’m hoping you might be able to save me from some unpleasant trial and error. Thanks again!

  7. Just my perspective here, but it kind of seems to me that sometimes the idea of really needing to do your own individual testing, one variable at a time, gets drowned out. As you mentioned, there really can be such a wide variation in response that is specific to each persons experience, what their goal is, and all the factors controlling their physiology that making generalizations rarely work accurately, and definitively, in every specific case. It definitely takes time and patience but the nice thing is a lot of the basic testing you need to do, and the monitors you need, are now pretty easy to get and relatively inexpensive, portable, etc. I think it can be said as well that really going through the process, doing the groundwork, and getting everything dialed in so specifically for your own situation can be a rewarding process in and of itself and really reinforces what you have learned. Also, if you have some extra resources to throw at the whole issue there really are some neat things you can test and do that only super elite athletes would have had access to before and Peter has outlined many of them here on this website. Especially if you live near a large university that has an exercise physiology department that offers services to the public. Just a suggestion here too about NK and fuel for something like ultra races you describe that you may want to consider is the old native tradition of making Pemmican which is a portable, stable source of energy. You can buy it already made or get plenty of recipes online to make your own custom blends. Even adding berries to it and all kinds of other interesting ingredients.

  8. Dr. Attia,

    CarbNite was previously mentioned (Norm) and I would like to know what you think of the “protocol”? There are some fitness advocates that endorse it as well.

    And conversely, (the statement that caught me by surprise) Kiefer claims that if you raise/spike insulin high enough (the overall concept of the protocol – glycogen being depleted), you actually burn fat instead of store it.

  9. Thank you for taking the time to write this amazing article, and just finished watching your presentation “An Advantaged Metabolic State: Human Performance, Resillience & Health” great stuff. I have to admit i geek out as well when it comes to ketosis and improving metabolic performance. I’m just someone trying get into optimum shape.

    someone else asked, “What are your thoughts regarding a ‘time window’ for optimum carb consumption following a “glycogen deficit” generating period of activity?” — and still be able to remain in a ketogenic state.

    you replied, “If you have a glycogen debt, you’re going to prioritize filling it regardless of timing, more or less. The “window” is a largely artificial construct, at least for most folks. It may be more significant for an IR person, where post-exercise IS in increased slightly.”

    what im wondering is… after the glycogen stores are depleted, will your liver work to create more glycogen to replenish the debt? and if so, how much time would I have to consume carbohydrates to replenish the debt myself before it would beat me to the punch?

    sorry if it’s a silly question, im just trying to understand it better. thank you, amazing work.

    • Main question:
      Consecutive anaerobic work –> gradual glycogen depletion –> Best behavior to be able to maintain anaerobic work (for example next days)???

      What about highly anaerobic workouts on consecutive days?
      If Glycogen is replaced as (Mr. Attia) explained, it seems to be even
      “necessary” to ingest more CHO than consumed on usual days in ketosis,
      in order to be able to do comparable anaerobic workouts on consecutive days.
      Is there a (natural) way (i actually don´t see) how the body can replenish glycogen after
      anaerobic workouts besides “consuming” some more than usual?
      If not, it seems that after anaerobic workouts the used portion of glycogen has evitably
      to be replenished through nutrition to be able to do comparable workouts again.

      What´s your opinion to that?

  10. Thank you so much for the time you spend on this great website.

    I’ve tried losing weight before via ketosis, after the first 20 lbs (water weight) I just didn’t loose any more. I don’t know if I wasn’t eating enough fat or if I was eating too much protein and fat? I was hardly eating any carbs, at least the ones I knew about. That’s why I wanted your thoughts on the following question and answer posted on the “Ask the Dietitian’s website, category “Fad Diets”. How does one know how much glucose is being provided from the protein and fat they eat? Do I need to invest in some sort of gadget to know if I’m in ketosis? I used ketone strips before but hear they might not be accurate. I’m so desperate to get my weight under control.

    Copied from “Ask the Dietitian’s website, category “Fad Diets”

    Q. Can you explain ketosis to me?

    A. In diets that contain fewer than 900 calories, all food eaten including protein and fat is broken down into glucose to provide fuel for the body. Protein and fat are very expensive fuels for your body. You can only convert 70 percent of the protein and 30 percent of the fat you eat to glucose. The nitrogen from the protein is excreted in the urine. This leaves no protein for repair or maintenance of muscles and organs. Also, in diets containing fewer than 130 grams of carbohydrates, ketosis occurs and your body starts breaking down muscle and lean tissue to provide glucose for brain and nerve fuel. Your body’s first need is for fuel. Your body’s use of dietary fuels cannot be changed drastically by altering your diet.

    Your body can and does take stored fat (as triglycerides) and incompletely breaks it down into ketones, which can be used as a fuel source for muscles and organs. To completely breakdown body fat, you need glucose and oxygen. If glucose is not available for fuel by your limiting dietary carbohydrates, your body learns to run on ketones, but your brain doesn’t. Your brain gets sluggish because it only runs on glucose. Your body starts breaking down muscle and organ tissue to provide the needed glucose for brain tissue. Protein contains glucose in its structure and it can be scavenged for use by the brain and nerves. Quick weight loss diets claim they spare muscle protein, but they don’t. A diet high in protein and low in carbohydrates does not spare muscle protein from being broken down, unless you eat enough carbohydrate. As you continue on a high protein, low carbohydrate diet, the amount of ketones increases and ketosis occurs. Ketones are very irritating to your kidneys and the kidneys try to get rid of the ketones through the urine.

    • The “fad diets” website needs to get some facts straight. I’d recommend a new reading source. Consider Phinney & Volek’s “Art & Science of LC Living” as a good starting point.

  11. Wow, THANK YOU for your blog and for being SO informative and going into detail. I am a female athlete (weight training – not pro, but for fun) living in South Africa and somehow, luckily, I found your blog. I am experimenting myself with very low carbs and high fat and also now going in NK. It’s all so fascinating. I am just LOVING reading everything you write. Keep posting. You are doing us all a wonderful service.

    I also noticed that after a heavy leg training session my weight almost always goes up. Females need to be very wary of the scale – rather we should eat and train to feel healthy.

    Thank you SO much. I really just wanted to say I appreciate your blog and I am reading as much of it as I can.

  12. Peter, any tips how one could calculate or at least try to “guess” how much glycogen is used during a weight training routine and/or high intensity intervals like tabata? In both cases body suppose to be burning energy long after the exercises, at least thats what Ive been told?

  13. All your experiences make me lol cause it sounds so much like me, but I’ve never tested I calculate correctly and I might do 50 gr carb most days but work out hard as well. My wife is now doing this with me. Any advice for female. She’s raced for about 4 years

  14. Hi Peter,
    This post is very interesting and opens up a whole new array of experiments a keto dieter can perform on himself/herself.
    I read in some places that bodybuilders who go into ketosis and out again every week sometimes use Alpha Lipoic Acid as a means of suppressing insulin spikes in order to go into ketosis faster (maybe also shortening adaptation time) and to better stay in ketosis.
    Is it possible ALA can be used with food (like an alka-seltzer) to “cheat” ketosis the same way you use long bicycle rides?

  15. HI Peter,
    I have a couple questions for you. I began ketosis for health purposes, supervised by physicians. I’ve always been small to begin with, so my health was my primary goal of ketosis, not weight loss. However, I actually have gained 10lbs of fat after being “keto-adapted.” I’ve always been very active and still remain active, resistance train 5-6days/wk. Do you have any thoughts on this? Although I feel great in many other aspects, I also have negative feelings as well such as I feel like my heart beats are more prominant and faster, I can’t seem to get my best strength back, I went from being cold all of the time to being hot all of the time. Is it possible that maybe I just have a different body type and maybe a different diet is better suited for me? I didn’t go crazy and eat all of the bacon and sausage I wanted. I’ve been eating eggs, coconut oil, grass fed beef, bone broth, organic chicken, olive oil, fish, grass fed tallow, very little veggies in the form of spinach and cauliflower mainly.
    My other question is, I believe in eating the way our ancestors did, in regards to whole, unprocessed foods, because I feel like we’ll never truly know the real answer in regards to what they ate. I believe ketosis was valid in regards to going days without food and depending on the area, seasons w/o veg/fruits. But I don’t really find it natural to go out of our way to consume tablespoons of coconut oil either. Do you see a problem with a diet combined of all of the healthy food groups? When I say this, I mean taking away grains and dairy (since they seem to be most problematic) and eating a variety of veggies, fruits, nuts, animal, fish, healthy fats. Does it have to be high carb or high fat? I tend to see a pattern with people who go on diets. That their inital diet was combined with many processed foods and that’s why they saw so many benefits while dieting. Because they took out the processed foods, not necessarily because of the specific diet choice. I guess my main question here is the subject on fruit. There’s much information out there that suggests it has the same effects on the body as does other unnatural sugars. I’ve spoken to a lot of people who do very well on a healthy high carb diet of which consists of lots of fruits, and some combined with many veggies, nuts, seeds, little fish/animal, but no processed foods. Do you believe this is setting up for future failure and problems? Maybe initially for those with insulin problems? Or maybe not so much after their body is healed from those? There are studies that show the harmful effects on fruit but then rebuttles that they were based on processed sugars and no actual evidence based on natural, whole fruit.

  16. Hi, Finally I found a good source of information for athletes practising LC diet.
    I have been on a low-carb diet for 2 months. In a few days I ill have my first mountain race (ca. 30 km, altitude increase +1320m, approx. time 3,5 h of effort). In my trainings runs for this event I recorded a very high heart rate (up to 180). Now I have a question about nutrition. In the book “Art and Science of Law Carbohydrate Performance” by J. Volek and S.Phinney, they say thay in trained athletes fat oxidation can be maintained above the level of 65% VO2max. However what will happen when I hit and maintain a much higher level of heart rate for a longer time ? Should I eat any carbs (potatoes, nuts and the like) before/during that race in order not to bonk or stay with fat only?

  17. Peter,
    I discovered this site a few days ago and have been reading everything on it every chance I get. Great stuff. Since you use a power meter I’m wondering if you use the Training Peaks software or are familiar with it? If so, do you think the kcal reading it computes for a ride is accurate and could be used along with my RC to compute my glucose requirements after a ride?

    • Yes, I use TP. If you use a power meter, kJ is approximately equal to kcal (but fluke of conversion), but say nothing of RQ, which you need to test separately.

  18. Peter,
    For any endurance athlete, I find this to be the best blog post ever. Especially for anyone that wants to utilize fat as fuel during exercise.
    Having said that, I just finished the Seattle to Portland Bike ride (203 miles in 16 hours) in 91 degree heat in one day. Brutal. Just Brutal.
    The day before the ride I was at a fasting level of 0.8 mmol ketone level. Good but great.
    I went in the the ride knowing at some point I would need carbohydrates but not sure when. So I bought and took with me foods that were fat containing and foods that were carbohydrates, like energy bars and shot-blocks.
    I had bacon and eggs for breakfast then started the ride. I felt great for about 75 miles then I lost power output and I had the intrusive thoughts of devouring anything sugary. I had to cave in and chow down a shot-block package.
    The rest of the ride was simply impossible without carbs. Which, after reading this post, is reassuring considering I can still be in ketosis after eating so many carbs. CONTEXT MATTERS. Not Sure what my RQ is…but it was obviously higher than .75.
    Peter, my question: How do I test my RQ? Do I need a university lab?
    Paul Arena

  19. Peter,
    I was wondering if you have heard of this “MuscleSound” product ( It’s designed to measure intramuscular glycogen content. It’s none-invasive technique is much more preferred for field use then muscle biopsy for obvious reasons. If you’ve already seen it then sorry. Just discovered the founder (Dr. San Millán) through a Twitter post by Tim Noakes. Makes a great case for keeping glycogen stores in an optimal range for high intensity athletes. Seem like it really is important to get Carbs in the system right after the glycogen depleting event. The question: how much is just right? Probably different for everybody.

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