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. Another great article. These are really helpful.

    Your meal of carbs, if it had a high insulin spike, might qualify as a leptin spiking overfeed used by some body-builders (e.g. John Kiefer’s

  2. I have what I hope is a simple question. Like you, the exercise I do is pretty intense, mostly high intensity interval training. I’m also a big fan of NK, throughout my youth and adult life eating this way has delivered the best results for me as well as the best overall feeling of wellness. The challenge I have is, if I follow a diet that keeps me in NK, one where the majority of caloric intake comes from fats such as eggs or meat, my cholesterol (total) soars into the 485 range with my LDL at 343. Everything I know is that this is unhealthy. Back to my “simple” question, is this safe (being at 485)? My goal is very much like yours, to balance my performance AND overall health and wellness.

  3. Interesting post. My quandary is this: while I’m a fan of NK, if we are to mimic the hunter-gather diet, wouldn’t we want at this time of year normally available carbs like berries, greens, apples, etc?

    • Perhaps, but probably depends on which geography to some extent, along with 7 other things I can’t get into without another 3,000 words.

    • The problem is, whatever fruits and vegetables our ancestors could find at this time of the year, they are not available to us any more. The apples we eat today contain much more sugar than anything you could find in the wild.

  4. This mishuganeh level of bike riding must create quite a stress induced cortisol output. Have you documented that?
    Very fascinating article. I have been recommending your BLOG to patients frequently to patients over the past two years as a very important resource to correct nutrition. keep up your wonderful work but take up less stressful hoobies. Have you tried free flight model aircarft or home machining?
    Paul HelmanMD.
    Evanston , Illinois

    • Yes but not neccesarily non stressful . Problem with free flight is that you have to chase the darned things cross country. Maching fine but wear safty glasses and keep fingers away from the spinning headstock.
      Anyhow keep up your very impressive work.

  5. Nice article Peter. The idea of “glycogen debt” is basically where I ended up in regards to my ketosis. I don’t sweat the numbers anymore. I can “feel” when I get below 0.5 mmol BoHB anyway.

    One interesting thing I was wondering if you noticed, I seem to have developed an intolerance for sugar now (fructose only?). During an ultra I accidentally took in some electrolytes that had some sugar in them and throughout the day I was nauseous. The same thing happened when I tried some sweet potatoes fries with which someone had poured honey and had the same reaction (the occasional 3 or 4 straight sweet potato fries do not give me any problems) . Do you experience some sort of sugar/fructose intolerance ?


    • Jason, VERY funny to hear you say this. I was going to write about this, but the post was already getting too long. On the day before the ride I reported on, I did basically the same thing, except I used much more fruit to replenish glycogen. Even though I actually rode stronger (e.g., higher power numbers, higher avg and max HR, faster speeds), my gut felt horrible by the last 30 miles. Hence, for the following day I said to hell with fructose, I’m going with predominantly glucose to replenish glycogen. In retrospect, this should have been obvious to me for reasons I will write about in the coming months that pertain to how our liver processes fructose and the ATP cost of doing so.

    • Excellent, thanks Peter. It is nice to know it was not just me.

      I had a thought that it might have to do with gut bacteria (?). As I understand it Candida comes from an overgrowth of the kind of bacteria that processes sugar. I wonder if prolonged ketosis kills off enough of the sugar processing bacteria that you no longer have enough to handle even a moderate sugar load ?

      I really look forward to what you write about the fructose. I guess I just need to stick with glucose for now. I am still having trouble gauging during a race when I really need to take in glucose. My last 50 mile run I just ran on 200 calories from a quest bar. Felt great all day but could I have been faster taken in glucose ?

      I am currently operating on the assumption that I want to minimize the flux of glucose across the cells that cannot protect themselves via GLUT4/insulin during prolonged exercise. Until I come up with some way of knowing when and how much glucose I can take in without upsetting anyone I will have to continue to minimize it…


  6. Hi Peter,

    Thanks for your timely post. I’ve been trying LC for awhile and have the same blood meter you do. Unfortunately, I haven’t been successful at getting into deeper levels of Ketosis on a regular basis. I have a food scale at home and at work – my latest attempt was 15 oz of protein food per day (~105 g) and “no visible carb”. I wound up on the bathroom floor with extreme constipation and a suppository 🙂 So the veg. is going back into the diet.

    If my fortunes don’t change I’m going to cut protein to 84g and possible go to two main meals a day. Some people swear by that but I can’t find any data to support meal frequency having an effect on ketosis.

    Keep up the great work – looking forward to the first research paper out of NuSI.

    Best Regards,

    • Eric,

      With regards to constipation, you might try adding magnesium to your system. The idea is to start with a low dose (say 200 mg/day) and increase till you reach bowel tolerance. This level is very individual and can be much larger than the 400 mg/day RDA. The body will take what it needs of the Mg and excrete the rest in your bowels. The excreted Mg will absorb water and bulk up your stools. Taking any electrolyte assumes you have normal kidney function. Whatever Mg is absorbed is a good thing, so you kill two birds with one stone. You will also minimize any issues with leg cramps.


  7. Peter,
    The whole point about the religious fervor is spot on. I can understand the reasons for it (we are all making wagers with our health about what the right science is) so there is lots of anxiety tied up with being challenged on our nutritional beliefs. Anyway, the thing I really appreciate about you and Gary Taubes is that it is all about the science.
    Nice post, btw.

    • Thanks, Paul, but I still wish nutrition could be discussed in a manner distinct from debating legalization of abortion of immigration reform.

  8. Dr. Attia, very well written article. I am new to nk, and I haven’t been able to read all of the blogs, yet, but I was under the impression that, when we are in nk, we are using stored fat instead of glycogen stores(or maybe I just misunderstood)?

  9. Hello Peter,

    First of all, thank you for writing this blog. While much of the material is over my head, it has given me much food for thought. I have a blood screening every year as part of my membership in a preventative health clinic here in Canada. Long story short, I have decided that at 46 I had to quit smoking (which I did 2 months ago) and I very recently started a low carb diet to kick start fat burning and this has worked. I suspect I am in ketosis because of the results of the ketostyx I’m using but I would like to track other markers and as accurately as possible. How often should I realistically test my blood for things such as triglycerides and cholesterol and should I test my glucose and bhb levels as well? It would be highly motivating to me (much more so than just losing fat) to be able to know that I’m actually getting healthier.


    Luigi Rocca

  10. Peter when you have time could you publish the powerpoint slides from your video highlighted in My Quantified Self, Part I? I find myself opening the video and fast forwarding through to find particular slides.

  11. Hi Peter,

    Is it possible to get into Nutritional Ketosis (say, above your 1.0 threshhold) while taking a statin drug to lower LDL serum level?

  12. You should charge for these posts. Amazing quality of content. Anyway, I quit racing years ago and consumed massive quantities of horrible carbs at the time because I thought it was required. Since then I do IF and eat very low carb. I started riding again, but I’m not carbing up and only bring water in the bottle. I’ve even done some rides during the fast and there is no distress. I’m not doing time trials and cranking out massive wattages, but I’m not noodling either. After reading Volek/Phinney on low carb performance, I’m convinced it’s possible to function well with fewer carbs than we’ve been led to believe, but I don’t know how well this will work when I pick up intensity. It will be interesting to see how you feel when you’re pumping over 300 watts. Good luck.

  13. Awesome training Dr. Attia. Wow! And you look in great shape.
    What’s your time for the 1.5K swim and 43K bike?

  14. The position/theory that obesity does not cause insulin resistance, but that insulin resistance causes obesity is ludicrous and fallacious with absolutely no supported legitimate empirical, statistical data or studies which have been peer reviewed by qualified professionals and academics. You may mean well but your position is just as valid (and amusing) as the half-wit Neurosurgeon Dr. Eben Alexander who claimed he “saw heaven” when every Neuroscientist and other Neurosurgeons specifically identify why/how his position was equally stupid and utterly false.

    By definition, science requires you LOOK AT FACTS AND DATA and then postulate a theory BASED on the facts and data. You don’t postulate a theory that shoehorn and cobble together cherry picked “facts” and “data” to support it. Please, don’t spread misinformation based upon kneejerk, “anecdotal data” which has all the relevance of 2 guys talking to each other and drinking from gallon jug on a porch.

    • John, I’m pretty sure I’m looking at more data than you are. I’ll give you a pass this time, but watch your tone. You’re crossing a line I have no time for. If you disagree with me, fine, but learn how to do so respectfully or go some place else.

  15. Hey Peter,
    I’ve been lifting very heavy weights on NK for about a year thanks to your blog. One thing I noticed in my lifting was that at first it seemed impossible to reach the same level of strength as I had when I had a carbo loaded diet. However, everything seemed to change once I started breathing heavily both during the exertion and inertia parts of the weight lift. This seemed so counter-intuitive to me, but when I tried breathing the “old” way of exhaling just during the exertion, my strength again dropped to pre-NK levels.

    What are your thoughts as to what’s going on here? Does my heavy inhaling and exhaling during the entire lift help me lift aerobically instead of anaerobically? Am I oxidizing fat more than glycogen, thus limiting lactic acid build up, by constantly breathing even with very heavy weight? I typically lift as slow as possible throughout the lift while constantly breathing. Also, I typically lift several sets of 5 reps with 105 lb dumbbells and 225 lb military presses. I’m 5′ 11″, 290 lbs., so I’m not like I’m a bodybuilder. My diet is about 70% fat, 25% protein and 5% carbs. Any confirmation or explanation on my freakish strength since on NK and breathing would be appreciated.

  16. Dr Attia – Can you comment on Quest bars? They seem to contain a large amount of carbs ( though mostly fiber) as well as sugar alcohols. I’ve been looking for a good bar for some time with no luck, so I often make my own.

    • As you note, most of the carb is soluble fiber. I like consuming them on long rides or as snacks, but I do need to be careful…I can eat them non-stop, if I’m not careful.

  17. Dr. Attia, I’m curious to know your thoughts about a correlation between NK and kidney stones; specifically whether you think the scientific literature supports the correlation.

    I found your blog and NuSci through reading G. Taubes work and reading about him. Fascinating stuff.


    • I think there may be some overlap, though I am unaware of any randomized data showing this. It seems like something addressable by electrolyte and mineral supplementation, which will depend on the type of stone being generated.

    • Mark, If this is a concern, you may wish to investigate potassium citrate. It is actually the citrate that is beneficial. It appears to be helpful for both calcium oxalate and uric acid stones. There is a prescription med, Urocit-K that you can check out. You can also purchase potassium citrate OTC. The decrease in stone formation with this is fairly dramatic. Look at the referenced studies with Urocit.

    • George N,
      Thanks. My question was more academic than therapeutic. My trainer is skeptical about NK but interested in observing my experience. Risk of stones is his latest bugaboo after seeing me lose fat without a noticeable decrease in energy or performance. I’ve never had a stone.

  18. Hi Peter,
    I’ve been on a low carb diet for a while know, but I don’t think I’m in ketosis. I’m really interested in experiencing the brain effect I’ve heard about. What do you recommend is the best way to do so? Currently, I basically eat all vegies except white potatoes (which, sadly, I suspect is what’s standing between me and nutritional ketosis.) Do I need to cut those out? Can I eat salad? Should I invest in a blood ketone meter? I know the choices depend on person, I’m just looking for some guidance or direction.


  19. This is fantastic. I love ketosis an it seems to work really well for me after my brain injury, however my sleep tanks after about 2-3 weeks so I want to add some carbs using this formula.

    How would I calculate and measure my power and wattage used in any given exercise, for example some sprinting or other similar types of exercise?

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