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. Appreciate your website! =)

    I’m currently following a routine roughly 3x per week consisting of alternating workouts:

    Workout A
    – Powerlift Squat
    – Olympic Clean and Jerk
    – Powerlift Bench Press
    – Dumbbell Row

    Workout B
    – Powerlift Deadlift
    – Olympic Snatch
    – Dumbbell Bench Press
    – Weighted Pull Up

    Each exercise is performed for 3 sets of 5 reps. For this program, I’ve been trying to remain in ketosis with starchy carbohydrates only after exercising. It’s awesome that right as I started this program, I came across your website. It’s been an invaluable resource!

    My question for you is, how many carbs do you think would be safe to consume after each workout? Right now, I shoot for around 100 g, but I think I’m doing as you say…overestimating how much glycogen I actually burn during workouts.

    Coincidentally, I have had trouble keeping blood ketone levels up. Thanks in advance!

    • No worries. I think my best bet would be to just find a good amount of carbs through trial and error using ketostix as a rough guide…and knowing their limitations.

      Do you have an article on your site which compares CKD- vs. TKD-type approaches? If no article, do you know of any good studies? I’ve been searching, but can’t find any that compare physical performance between the two (and also vs. SKD).

  2. Peter hi been attempting a higher fat diet that is lower in carb since I came across your ted talk and your blog. Not the easiest thing to do in Dubai and now Nigeria. It has also gotten me into doing lot more nutrition research than I’d have preferred but one must learn. My body type and weight gain story is similar to yours though I exercise ONLY lightly these days but the trend (weight) has been steadily up over the last decade as I’ve grown older (now 37). I’ve lost 10 lb or so in the last couple of months. dropping to just under 200lb for the first time in 6 years or so. Through the research i’ve gotten very curious about which oils are better than others for frying. I’ve been frying my (and my kids) eggs in butter but thinking about trying palm oil or coconut oil. I’ve not found a great source to help parse the “oils” world and the pros and cons. Can you suggest a resource for this if you’ve looked at it? Or share your thoughts. Best.

  3. Hi Peter,

    Thank you for your great efforts!

    My question is somewhat in line with this entry. I was wondering, can ketosis and (hereditary) kidney disease co-exist? My education (medicine) is a lie, my doctor has no clue, and dieticians… well, you know. And I’ve been reading as much as I can recently, but this topic is skipped everywhere (or buried under the ketosis is bad for your (healthy) kidneys myth). Lately I’ve just been easing out the carbs after two failed attempts to maintain ketosis.


    • Not sure which kidney condition, but I guess the question is what additional demands does a KD place on a less functional kidney? KD does not require additional protein, so I’m not sure the concern.

    • Thank you for your reply! The condition is Alport Syndrome.

      I must admit, I was a bit skeptic when I heard about KD. I well understood the benefits, but I could not see how it could work for me personally. As you know, low protein consumption is recommended for kidney disease, as (some?) amino acids increase the GFR. I was actually delighted when I saw the ratio’s for KD, although it still is a little too much, if you compare it with the recommended 0,8 grams/kilogram body weight.

      However, what actually worries me is the combination of the ketone bodies, which as far as my knowledge goes increase GFR, the -too high still- protein consumption, which increase GFR and the heavy dietary electrolyte load.

      I am afraid the load on my kidneys will be to much. My attempts failed due to extreme fatigue (which could be normal in transitional state). The reason I decided to quit was that the foam layer on my urine (my subjective way of measuring my kidney function, heh) was getting too big.

      I was wondering what your thoughts on kidney load where!


  4. Hey Peter,
    I just scheduled a doctors visit for my mother who is having, what I think is, terrible bouts of reactive or regular hypoglycemia during the night or mid morning after fasting for a while. It has gotten more frequent since trying to adopt a low carb lifestyle. Myself and my Dad have responded well to the Keto diet and we feel great. What types of tests should we request from the Dr.? I say glucose tolerance test and insulin blood levels. My thought is that she can’t access her fat stores. When fasting overnight she gets the epinephrine surge and then gets the symptoms. Any thoughts would be awesome.
    Keep up the great blog posts.

  5. Hi Peter, Such a timely article for me, thank you. I’m 7 days into ‘low carbing’ and still very much a newbie but excited about the possibilities. I’m hoping that I may be one of the lucky ones who can use fat as the primary energy source during endurance cycling. I currently do 200 miles of cycling a week, 100 miles of commuting ( low level stuff) and 100 miles with my cycling club. On the club ride this week I completed the distance, however was very slow and got dropped out the back. I accept that as this was my first week of low carb my body is still learning to use fat for energy.

    Question is, how long might this take, or is that just impossible to tell. Second question, if I read your article correctly then is it ok to eat a higher carb amount on big club ride days, especially just after the ride. Third question, is oatmeal ok as a carb source just after or during a ride ( perhaps in the form of a flapjack). Apologies for so many questions, just keen to do this right. Thanks so much for reading.

    • Kath,

      Basically, it sucks for everybody when they are first getting adapted. You just need to accept this. The fact that you can finish a 100 mile ride with your club during adaptation is actually quite remarkable. I’d guess it’ll take you two – three weeks to get adapted, though there may be ongoing adaptation after this. My suggestion is that you do not “cheat” or play the games that Peter is playing with carbs until you’ve been fully adapted for a while, otherwise you may just delay the process.

    • I am primarily an endurance focused athlete and the transition to low carb, which I began back in June of 2013, has been very difficult for me in terms of running and other aerobic performance. However, I am stubborn, and because I was seeing so many other benefits, I continued to struggle. I took to heart all the advice on the blog, monitoring protein intake, increasing salt intake, introducing BCAAs, but nothing seemed to make a significant difference. Recently I noticed that I am losing more hair than usual, and based on my own research, this is not unusual on any diet regimen, particularly low carb, and generally corrects itself once your weight stabilizes, when taking into account hair growth cycles. Not willing to wait and see, I began supplementing with a “hair, skin, nails” formula, which is primarily B vitamins and C, not coincidentally, I think, your classic “stress” vitamins. I saw a noticeable improvement within a few days. I think the doctor could comment better than I could theorize, as to all the reasons why this may be true, but I think it is worth a try, and, in any event, would not be harmful.

  6. Hello Peter,

    Thanks for the great blog. This is fantastic information.
    I have been looking through the blogposts for an answer but have yet to find.
    When do you supplement? All in the morning or split through the day?


  7. Hi Peter,
    I’m very much in doubt as to which diet is healthier LCHF or IF ie. one meal every 24h?
    I’m not trying to loose weight or run a marathon I just want to be as healthy as possible
    thanks for a great site!

    • some studies suggest that benefits of NK and IF are overlapping but not the same, hence you probably have to do both. maybe you could just do one and supplement some stuff like resveratrol if you are after some specific gene expressions.

      however – why not have both? in practice, anyone doing LCHF should automatically be fasted regularly (less hunger) and hence reap both benefits partially.
      I do (without any difficulty) 24h fasts at least weekly, most days I do 18/6 (=2 meals within 8h, usually lunch and early dinner).

      I do IF as well to compensate that I cannot work out as much as I would like (5x)

      maybe get your inflammation markers checked as a means to control your lifestlye, however all I did came down with non measurable values.

      get you genes tested if you are apoe e4 with one or two copies I belive you have to

  8. Thank you Dr. Attia for another great post. I know that you are big into objective numbers in your n=1 study, but my question is this: what –if anything– do you notice on a more subjective level when you slip out of NK? Does the birthday cake make you feel loagy? achy? sleepy? no different? How long does it take you to recover? Do you track your subjective emotional, intellectual and physical energy levels daily and if so what have you noticed in relation to the lab #’s and diet.

    Thanks again for all the time and effort you put into this blog. It has been of immense value to me as I conduct my own n=1 experiments.


    • Quite a bit, Rob. I feel pretty lousy when I fall hard out of NK, usually for a few hours, but it depends on the demands I put on myself, too. For example, if I wake up with BHB of 0.4 and I’m about to hop on my bike for a long ride, the first 2 hours will hurt until my liver starts making enough. I don’t track emotional, though I think I have too many confounders.

    • Rob,

      As another data point, I feel like dirt when I fall out of NK.

      I lost 35 pounds on a LCHF diet, and now have a BMI under 25. This summer I decided to allow a few more carbs in my diet, but I did it the wrong way. Instead of a sweet potato or a slice of multi-grain bread, I’d have a few light beers, a few slices of pizza, or some cheese and crackers (which those around me were having).

      The result was my insulin resistance returned with a vengeance. I was back on the energy roller coaster, and the lows were murder. In the middle of the afternoon, or in the evening an hour after supper, my energy would hit the floor and I’d want to crawl off for a nap. That didn’t happen when I was in NK. I’d also run out of gas early on my hard (relatively) hour-long bike rides.

      And the cravings came back — especially in the evenings, as my blood sugar dropped and my body was telling me to eat carbs to bring it back up.

      Volek says that getting and staying in NK is like climbing a big sand dune — much easier to stay on top, than to keep sliding down and climbing back up. I have give a big “Amen” to that.

  9. Just had a brief read/musing about the effects of sirs on exercise physiology. Thank you for mentioning it, any particular sources that you might recommend?

    • Everything I learned about SIRS I learned during 5 years of critical care medicine. The classic Marino text was very helpful, but no mention of exercise, of course, just sepsis, burns, cardiogenic shock, etc.

  10. I am off to buy the September issue of Scientific American in the morning. Looking forward to reading about the work of you, Gary Taubes and NuSi.

  11. Well after years of reading all a lot of nutritional studies and listening to all different experts talk from Dr. Ornish, Dr. Furhman, Dr. Willet and of course your work Peter (which finally put all the pieces together) I have developed framework for nutrition which I present here:

    What did are ancestors eat and can that help us develop the an optimal healthy diet?

    What did your ancestor’s truly eat? Everything they could. Yes this means grains and beans when available (not year round like today), plus fruits, vegetables, meat, eggs, insects, fish, and rotting/fermented foods. They were constantly battling starvation and had to make use of all sources of food available to survive. This is key, most of the time our ancestors would be in a starvation/survival/fat burning mode. This survival mode is the healthiest state to be in. Every animal lives longer on a low calorie diet or by someway tricking the body to think it is in a low calorie state. The key for optimal health is being in this survival/fat burning mode while at the same time maximizing nutrient intake. Okay so let me explain why I agree that a high fat low carb diet is optimal.

    What our ancestor’s ate grain and beans?

    Yes they ate grains and beans, but the grains looked more like teft and for beans look at the wild ancestor of soybeans it doesn’t have the nice plump seeds of todays varieties. Grains were a lot lower in carbohydrates and higher in protein when our ancestors lived. They didn’t have the plump wheat, corn, and rice of today. Even vegetables we think of today as low in carbohydrates (broccoli, kale, and spinach) are nothing like what our ancestors would have come across. Fruits are the same, sweet apple varieties are a modern invention along with most sweet fruits. Crab apples are a lot closer to what our ancestors would have come across. Todays plants have been breed for higher yields and sweeter tastes. Lets face it todays food tastes a lot better then the tough, bitter, small wild plants of our ancestors. This increase in carbohydrates in plant foods available to us today is a major reason why even eating a whole plant based diet today, I would argue, won’t give you optimal health unless you eat a low fat, calorie restricted diet as well and hopefully you will see why by the end of this post.

    Why are carbohydrates the important nutrient to a healthy diet?

    To me a healthy diet today its all about insulin control and the way to control that is through carbohydrate manipulation. When we eat a lot of carbohydrates, insulin levels go up, fat burning goes down and our metabolism switches form starvation mode to reproduction/fat storing mode. It makes evolutionary sense that carbs would be our bodies fuel of choice, it can’t be stored, produces a lot of energy and because in nature if you have access to them it means food was abundant and it time to put on weight and reproduce. Yes I think we evolved to get fat when a lot of carbohydrate dense food was abundant. This is not a healthy state to be in and is the cause of your current health problems. We are eating a diet that is meant for us to quickly reproduce and quickly get out of the way of the generations to come.

    Why would our ancestors burn fat, their primary storage fuel first, when carbs were plentiful?

    It wouldn’t make any sense form an energy stand point. It is a lot better strategy to burn carbohydrates and store any extra calories as fat from any source (carbs, proteins, fats) for lean times, which was most of the time. We did not evolve to burn carbohydrates as our primary fuel source all the time. We did not evolve to produce that much insulin or to be efficient at metabolizing fat when on a diet rich in carbohydrates. Our bodies have evolved to store calories under these conditions. Our bodies are able to run on a high carbohydrate diet, but to do this for optimal health we then we must limit our fat and stay in starvation mode through reduced calories. This maintains us in the starvation state, our bodies are burning all the calories we are consuming and the little bit of fat metabolism that is still activated is able to deal with the small amount of fat in our diet without negative consequences.

    We are adapted however to get our nutrients through plant I would argue. Lets face it our distant ancestors ate a lot of plants and our body physiology is meant to eat a diet high in plants. There are far more protective compounds in plants than animals. The one thing I have not seen supported in the scientific literature but wonder, is if our bodies are better at regulating essential nutrients through plant food than animals foods. Iron comes to mind. If you have high iron levels your body can absorb almost no iron from plant foods or if you are deficient it can absorb almost as much as meat. Another one is beta carotene, our body will turn it into vitamin A if needed, but if you have enough vitamin A it will keep it as beta carotene/host of other carotenoids that are beneficial to health. However Vitamin A in excess is very hard on the body. Another strong piece of evidence for our ancestors eating a diet high in plant food is our inability to produce vitamin C which almost exclusively comes from plants. Only exception I can think of is the narwhal whale.

    There are few exceptions of nutrients that are better obtained from animals that show meat is an important part of our ancestors diet. Omega 3 is one. Humans are not great at turning plant based Omega 3s into biologically active forms and hence must have come from somewhere. I conclude that eating insects, wild animals, and sea food would have supplied enough omega 3 that there was no evolutionary advantage to developing the ability to convert the inactive form found in plants into biologically active forms our bodies require at faster rates. This supports humans eating a diet that included meat. We also didn’t eat as much omega 6 (grains) which blocks our ability to form the biologically active forms of omega 3. There are other high energy molecules that I think improve human health that are only found in animals as well.

    Okay what can we take from the above to develop an optimal diet today?

    I think the goal of a diet should be to maintain your body in the survival/starvation/fat burning mode. If this is true what is the best way to accomplish this goal? Well the easiest way to stay in the starvation mode is to starve yourself. I think everyone would agree that this isn’t sustainable or desirable, yet it is what people on low calorie diets do. It is also what you would have to do on a low fat diet to make sure you burn all the carbohydrates you consume to prevent excess getting turned into fat. The other option is to not eat carbohydrates but instead fat (thank you Peter for introducing this to me!). This tricks are body into thinking we are in a starvation situation as there are no carbohydrates to burn. In this state our bodies really kick in to survival mode and are able to deal with a lot of molecules that have negative health consequences under a high carbohydrate diet, i.e. cholesterol. The wonderful part is we don’t have to starve ourselves!

    Okay so we want to eat a high fat low carbohydrate diet what should we eat?

    Peter you do a great job of explaining this and have a far better grasp on it than I currently do so I’m only going to say a little bit of what I think that I have yet to come across.

    I would argue that it is important to try and eat nutrient dense animal foods. Eat organ meats, marrow and other parts of the animal that have a lot of nutrients.

    I would still argue that we should really emphasize plants foods (ie nuts, beans, veggies, fruits and possible a tiny bit of grain now and then. Yes I love sushi too!) and try to maximize the amount we eat to get all the health benefits from them. Our goal in selecting plant foods should be to eat foods that are very nutrient dense and have a very low glycemic index/load. Goal is to keep are carbs and therefore insulin in that target range that allows most of your metabolic needs to come from fat but still gives us the phytonutrients only contained in plants. Peter’s finding of being able to eat a high amount of carbs after intense exercise could be used to be to eat more fruits and other high glycemic foods that have a lot of health benefits.

    In conclusion I feel we are trying to mimic our ancestors diet however, with todays abundance of food we have to opposite problem of our ancestors in that we are trying to figure out how to stay in a starvation/ fat burning mode that their environment naturally forced them to be in. They were able to eat everything and anything they could but I feel that data supports that they just didm’t have access to the high glycemic foods (or not for long periods of time) of today so it was not a problem for them. Today we have to use modern nutritional science to figure out the best, most sustainable way to keep ourselves in this survival mode while we maximize the nutritional content of our diet.

    Okay I wish I could have posted references to all this but I don’t have time/will power. Also I didn’t know where else to put this and I think it kind of fits in because it kind of shows why we can’t have ketones and carbohydrates, unless we are of course in a glycogen deficit. Sorry for the ramble hopefully someone finds this useful and possible use it as a way to show that both high fat and high carbohydrate diets are healthy, it just depends with one you prefer.

  12. I found some interesting studies via google scholar. Likely I will get the idea between unlocking the pay wall, the Marino text you mentioned and some endless reference reading. I wanted to mention that I am having great results with nk and my own training. Thank you

  13. Dr. Attia, I’m curious to know your new findings on the connection between diabetes and obesity after seeing your TED talk this summer. Anywhere I can find more information on this?

  14. Dr. Attia, I’m trying to understand the relationship between a bomb calorimeter and energy produced in the body as part of the “a calorie is/isn’t a calorie” science discussion. Since our body doesn’t produce energy through instant combustion, rather through a slower change of reactions that may end in combustion, shouldn’t we say that at best a calorimeter measures the potential for energy release within the body? I mean this question from the point of view of the calorie is calorie camp. Since there are so many steps before energy release in the body, meaning that the energy may never be released (say, undigested food passed as waste), there is caloric potential, but I can’t figure out how putting the food in the mouth is assumed to be equal to putting it in a calorimeter.

    If it only measures potential, then all we know from a calorimeter is the maximum energy possible to extract from this food. To find out how much is actually used as energy, we would need some sort of tracer in the body along with the food to truly measure the food’s impact, right? Until then we’re just guessing based on proxies and self-experimentation. Again, according to the calorie is calorie camp.

    I am happily drowning in the research but some reassurance that I’m barking up the right tree would be helpful. Thank you!

    1980: Earliest note I see of imbalance between calorimeter and human energy expenditure
    Energy balance in man measured by direct and indirect calorimetry

    1988: Earliest questioning I see of calorimeter validity for human energy expenditure
    Theory and validity of indirect calorimetry during net lipid synthesis.

    I see that 1988 paper is cited by Dr. Kevin Hall, who you’ve mentioned:

    Recent research by USDA that calls calorie count for pistachios and almonds into question:

    • A bomb calorimeter measures total (potential) energy contained with the C-H and C-C bonds of organic matter. But there are several fates for that energy when we eat it. Under “normal” conditions, most of that potential energy has one of two fats: 1) “kinetic” energy — i.e., gets turned into ATP by the body, and 2) more “potential” energy, as stored energy in the body (fat, glycogen, and even muscle if you think about it). Some may leave the body (e.g., stool, urine), which is relatively straightforward to check, but rarely amounts to much outside of massive nitrogen losses (urine) or steatorrhea (stool).

    • Are there not other uses of those bonds in the body?

      Gut microbes take their share. Tissue repair, cellular functions, secretions. Shouldn’t that affect calorie count by detracting from ATP and fat storage?

      • Absolutely, but those take place within the body, which we define as a closed system. Tissue repair and the other things you list still require converting the potential energy of C-C and C-H bonds into other sources of energy. This all requires ATP. So while a bacteria may use up some of this energy doesn’t change the fact that it’s being used up inside the system. E_in = E_out + E_stored. (E_out includes “work” and loss)

    • Okay, thanks for the clarity. The calorie is calorie camp would still have to explain the more recent research that measured the inconsistency in counting calories.

      This 1990 study shows that doubly labelled water measured energy expenditure as 15% less than room and other calorimetry (sample size 4):
      Comparison of doubly labeled water, intake-balance, and direct- and indirect-calorimetry methods for measuring energy expenditure in adult men

      This recommendation to the European Union suggests calories off by up to 25% (by Geoffrey Livesey, an author of the 1988 study, who should probably be considered the archetype of the calorie is calorie camp):

      I see other recommendations such as that USDA one I posted that calorie count may be off by as much as 25%.

      So that even according to the calorie is calorie camp, calorie count should be reduced by 15%-25% after adding up food calories for the day. And even that is just a guess because energy use can only begin after digestion, so at the very least stool would have to be checked. Basically, a more precise presentation of their argument might be “a calorie whose consumption is measured by doubly-labelled water is a calorie” or “we estimate that a calorie as defined by Atwater reduced by 15%-25% is a calorie.”

      Not that it matters practically, but helpful academically to me to know that they don’t necessarily understand their own position.

  15. If I had a dollar for every time someone said carbs on this comment thread I’d be rich 🙂

    I prefer replacing my glycogen stores with protein. I crave it (and not bagels) after a workout. I do have to be careful though as it would be easy to eat two pounds of brisket instead of 8 ozs after a long bike ride and throw myself out of ketosis. A bonus is that the next day after a hard workout and a modest refueling with protein I am in the ephoric range of deep ketosis.

    I love going here to learn as you have indepth articles on intense exercise (and so many more keto topics) and the ketogenic diet. I see this no where else but in the books of Phinney and Volek. So, thank you, thank you!

  16. Peter , Do you think this paper could suggest that low amounts of things with fructose , like small amounts of fruit eg berries could be a superior carb on a keto diet ? I am keeping net carbs around 20 to 30 grams , but feel good when they include some berries ! I feel stronger ( more repetitions in say chin-ups ) and have more endurance in things like running.

    if fructose does not spike insulin as much and can cause a three fold increase in glycogen synthesis would it be an advantageous carb on low carb and keto diets?

    This caught my eye from this paper

    Fructose, through its metabolite fructose-1-P, has been shown to have catalytic effects on hepatic glucose metabolism by increasing glucokinase activity(,3). This mechanism has been shown to relate to an approximately 30 % decrease in hepatic glucose production under hyperglycaemic conditions in type 2 diabetic subjects(,3) and an approximately 3-fold increase in glycogen synthesis by 13C NMR spectroscopy under euglycaemic conditions in non-diabetic subjects

  17. Why do we need pre-event meals (morning of) and why does their composition matter? I am reading your post with the selfish question of what to eat the morning of the Chicago Marathon. If a) my diet leading up to the event has been sound from a NK standpoint, b) my body will largely be fuelled by my fat stores during the race, and c) carbs will be provided by sucking back UCAN pre-race, is there any substantive reason to choose scrambled eggs over (sugar free) ice cream at 5am? Or, is there a preparation for this extreme stress that the morning meal assists with – while preserving the benefits of NK?

    • My general “rule of thumb” is to consume nothing before rides of <50 miles (which probably translates to a run of 18 miles or so), provided BHB levels are over 1, and preferably 2 mM in the am. BUT, and this is the caveat, it is highly dependent on the output. I've done VERY easy 80 miles on nothing but water with no meal since 7 pm the night before. But if I'm going to burn some matches, I like to get some protein and fat on my stomach, and I need glycogen replacement, starting around hour 2. In the end, this is something to figure out personally during training. I love scrambled eggs cooked in coconut oil because it's very ketogenic. But so is keto-ice cream. I just don't crave sweet stuff in the morning, but I do crave salt. Chicago is at least a month away, right, so I think you can try out a few different pre-race meals over runs > 10 km.

  18. Many of the questions and answers here are very insightful, keep it up! Your work is greatly appreciated and is already improving the lives of many people, I am absolutely sure of that.

    You wrote this:

    “Just read a review article on this recently. No evidence post-lift CHO plays any role in muscle synthesis. Protein is sufficient.”

    I find that VERY interesting. I thought insulin was one of the most important anabolic hormones. I was actually going to ask how to use the anabolic effects of insulin despite a low carb diet before I read that comment. Does that mean that the only advantage of carbs is that you can exhaust a muscle to a higher degree? Does the anabolic effect max out on low insulin levels?

    I would be interested in that article if you still have the link!

  19. Reading this :

    “A CRITIC AT LARGEMAN AND SUPERMANIn athletic competitions, what qualifies as a sporting chance?

    I thought it was topical, especially where he talks about competitive Biking.

    In NK for 8+ months now, I often wish I could monitor, manage and manipulate, in real time, the factors, as Malcolm talks about, that go into an endurance event(running for me). This may be a few years away.

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