Ketosis and Athletic Performance: More Than Fat Loss


The above video is a presentation by Peter Attia, M.D.

His talk is somewhat technical, but I always write blog posts hoping 20,000 people will *love* them, not that 1,000,000 will *like* them.

In this presentation, you will learn (in my words, not Pete’s):

- More about nutrition than most MDs learn in med school.
- How ketosis-adapted performance can aid fat loss and high-altitude resilience.
- Why the calorie estimates on treadmills and stationary bikes are complete BS.
- The three primary systems of energy production and basic organic chemistry, both of which aid understanding of all athletics.

Even if you struggle a little with vocabulary, the first 30 minutes are well worth watching a few times.

This talk made me immediately want to jump back on the Cyclical (or “Cyclic”) Ketogenic Diet (CKD), which was conceptually introduced to me in 1996-1998 by the writing of Lyle McDonald, Dr. Mauro Di Pasquale, and the late Dan Duchaine. It’s incredible for simultaneous fat loss and lean muscle gain, though perhaps needlessly complicated for non-athletes.

I usually limited the carb-reloading period to 12-18 hours after a glycogen depletion workout on Saturdays, though I experimented with moderate Wed night carb-ups while training for sports like kickboxing.

If you’ve experimented with ketosis, what was your approach and experience? Pros and cons?

For additional reading, I suggest the following posts by Dr. Attia:


Odds and Ends:
This week, I’m using my birthday to change the world with @charitywater. Please click here to take a look. You could do the same.

Posted on: July 30, 2013.

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158 comments on “Ketosis and Athletic Performance: More Than Fat Loss

  1. I have dealt with a lot of keto diets in my day both personally and with my patients.

    I have a broad spectrum of patients from extremely obese to bodybuilders. I have seen it help the most metabolically diseased folks and also help a handful of athletes.

    I have also seen it destroy the metabolisms of healthy patients as well causing some of my obese patients to have major thyroid issues and women to lose their periods. Many of my athletes lose muscle and strength as well.

    It is a powerful too but should be used as needed. Folks should be very careful and be in tune with their bodies.


  2. I am fairly familiar with a ketogenic diet as I train and support physicians to implement a ketogenic protocol for weight loss, but primarily to address metabolic syndrome.

    I’ve been living an extremely low carb ketogenic diet for the past 4 months that I have been combining with a daily intermittent fast of typically 18 hrs up to 21. I am loving living in ketosis. I have yet to experience a downside.


  3. I’m a marathon runner and this video really piqued my curiosity. I’ve hit the wall (bonked) so many times and would love to somehow avoid it – or at the very least put it off till mile 25 :) Gonna incorporate this into my current training cycle.

    Dr. Attia mentioned on his blog that ketones could also be increased via supplements (not raspberry). Which supplements help to increase ketones?


    • Medium chain triglycerides – they don’t digest like normal fats, they basically slip straight through to the liver and quickly metabolise to ketones and stuff.

      Coconut oil is full of them, or you can buy MCT oil which is a concentrate and without the coconut flavour – actually as far as I can tell it’s completely odourless and tasteless.

      I’ve been intermittent ketogenic for a couple years now and never really noticed MCT oil doing much for me even when shotting a few tablespoons of it, however coconut oil gives me digestive issues – oddly enough it’s the other way around for most folk as far as I can tell.


  4. I think everyone should be skeptical just from a quick defense protocol. My GF is constantly (every week) tossing new “diets” over to me to evaluate, so sad.

    However, having said that, if you have read Timothy’s books 4HR WW, 4HR Body, and 4HR Chef, and watched Diggnation, and watched Foundation, and watched the “Random” podcast, then you can gain a far bit more contrast to what Timothy is blogging about.

    I am always skeptical of anyone’s claims about anything remotely related to diet, exercises, or even health in general. I’ve personally lost more than 150 lbs, not even using Tim’s methods. Does it mean my program was right, or even portable to everyone, of course not. Be skeptical and question everything, please.

    This is a great post, and Tim, thanks for adding this video. (I watched the whole thing and it was valuable to me).

    I have done experimentation with supplements and their behavior for years, and was more than accepting when I read 4HR Body and saw what Tim was doing. Simply incredible, and I was jealous to say the least.

    This info in this video is not only relevant, it truly is ground breaking. If i had a 100K to spare I would be investing in Peter’s foundation right now.

    Timothy F, thank you for everything you have done so far and all that you continue to do.


  5. Very interesting presentation! He left me with several questions:

    -what was his fat breakdown? What is his percentage saturated/unsaturated/etc?

    -As per my experience, ketosis leaves you HUNGRY. 4000 kcal/day sounds about right. How did he deal with the immense amount of kcal required?

    -Ketosis also leaves you with an intense desire to binge cheat (bonk). How did he deal with that without blowing his diet?


    • Roddy says “Besides carrots and salsa, I never eat vegetables, mainly because I’m lazy and I can’t think of any reason why I would want to include them in my meal.”

      As a carnivore I agree with the that, but he outlines a typical day’ish of eating which includes 1-2L of milk, 1-2L of orange juice, some white sugar, 1-2 Mexicokes (whatever they are)? The rest sounds like actual food.

      To think a ketogenic diet interferes with cellular respiration compared to up to a gallon of milk and OJ and sugar and soft drinks (?) is kinda bananas innit?


  6. Disappointed I’m reading this late. I met you at Google and asked about intermittent fasting if you recall.

    I’m curious how fasting affects body composition. From personal experience have been doing intermittent fasting with low-moderate exercise for well over a year with paleo. Recently, as soon as I switched to a full day fast after my cheat day I noticed my body changing composition, not weight, but I felt I developed less abdominal fat.

    I’m curious on trying different fasting methods (many here in bbc documentary) and their effect on myself and others. Would be a great crowdsource project Tim if you gathered groups of folks and tried fasting methods with those folks and then based on feedback had them try another method. Questions I have developed for myself based on my recent fasting experiments:

    -Does when I eat/fast matter more than what I eat?
    -Is a method where I fast for full days more effective than intermittent fasting?
    -How does all the above affect my biometrics?

    I have genes, per 23andme, that lend themselves to high triglycerides and carbohydrates and my number 1 disease I am subject to is coronary heart disease (56.7%).


  7. Hey Tim,
    not talking right now about this topic but…
    Are you in Recife – Brazil?!?!?

    I swear to God that I’ve seen a guy that looked so much like you last week in a steakhouse restaurant.
    I’m a BJJ fighter here in my city, so if you are really here for a time and want to train in our gym you are very welcomed! =D
    You have my email if that was really you! hahaha

    Anyway, your book changed my life! Thanks for sharing everything you do! :)


  8. I have experiemented with low carb diets. It takes some getting used to especially when you train hard. I usually workout 4-5 times a week, including endurance training and find I need the carbs just to fuel my workouts. I guess if I was less active than I wouldn’t struggle so much.

    I now follow a modified ‘carbohydrate cycling’ diet which enables me to focus on vitrtually no-carbs on non-training days and medium carb intake on training days. It works well for my needs and is sufficent to encourage ketosis. I’m down to 8% BF and energy levels are fine. I guess you have to experiement a little to find the right nutrient intake for your body type, size and energy needs.


  9. Admittedly, I do not suffer with excess body fat. I am an avid practitioner of mountain biking and hit the weights twice in an average week (slow movement, 9 lifts, whole body per work out). For the sake of full disclosure, I may have a genetic predisposition for low body fat and general health.

    While I do not argue against the short-term solutions offered by the high-protein, paleo-esque diet – I do believe it is worth asking a simple question: how do I weigh my long term health against my desire for immediate satisfaction? As an athlete, I have enough anecdotal evidence to suggest that high-protein diets (Paleo, et al.) will produce phenomenal body alterations in the shortest amount of time. In our days roaming the sub-Saharan continent, access to high-protein foods would have been intermittent. These diets likely prey upon systemic frameworks targeted at taking advantage of these occurrences to generate growth and fuel the androgenic system. However, I do believe that there is continual evidence to suggest that diets aimed at utilizing these systems over long periods cause the body to deteriorate over the long term. Remember: evolution does not care about humans in their late 20′s or 30′s. Once you and your prospective mates produce 1.1 viable children, you are considered an evolutionary success.

    As Mr. Ferriss is sure to point out, time is our most precious resource. I agree whole-heatedly with his sentiment. Therefore the question of health and diet must be re contextualized: how do I weigh my desire for immediate results against my goal of “useful longevity”. I would suggest that unless you are a professional athlete, you consider our unnatural access to raw “superfoods” from around the world. By leaning toward a nutrient rich, raw food diet you may see a marked delay in immediate muscle building or fat loss – however I plan on using this plan to continue athletic performance into my 90′s and beyond.


  10. 2 questions regarding athletic performance & ketosis.

    I follow SCD, Effortless Superhuman and play a crazy, crazy sport called underwater hockey ( , the first 2 min should give an idea of the intensity and game play) and I suspect ketosis might solve one of my biggest problems.

    A weighted puck is pushed along the bottom of the pool by people wearing fins, masks & snorkels. No scuba gear allowed. One of the keys to great play is an excellent breath hold. Being able to stay under 20 sec is good. 30 secs? Never mind 80-20, it’s more a 98-2 kinda situation. The pay-off in a 10 sec breath hold at max intensity would be huge (and so would being able to do it again after 5 breaths). So I’m really keen to sort that out.

    Would a state of ketosis help me get that extra 10 secs? From what I understood in the talk, it might but all Dr Attia’s cases were for 60% intensity over longer periods of time or for high intensity with constant access to air (plyo stuff). In underwater hockey the effort to propel yourself (+ puck) at speed makes for high intensity without O2. Sometimes you stay under for 20 sec working as close to max, come up for 5 breaths (sometimes there’s only time for 1) and down again. On perceived exertion scale: Often not able to talk (even if it hadn’t been underwater I’d be too out of breath). If I manage to talk, it’s hard to do so.

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

    My second question is am I understanding him correctly if I say that ketosis helps with post exercise recovery? Weekday practices are Mon, Wed & Thurs nights. On Thursdays my in-game performance is down (subjective observation: I feel tired, can’t out-swim poeple as often and bottom time is shockingly bad) and on Friday mornings I struggle to get out of bed. Would ketosis improve the kind of recovery? I’m currently playing around with when I cheat but so far no noticeable improvements.


  11. Awsome video tim, thank you for sharing. I honestly enjoy learning more about the impact of nutrition on my body. I recently started a routine to change the way I eat to fuel my body. I got your 4hB (& 4HC) and planning to change and tweak my diet, in addition i am also interesting to follow the concept behind Dave Asprey´s Bullet proof diet. Though I must admit I get overwhelmed sometimes with the information there is.


  12. How can you guys stay in ketosis if you load with carbs at all? It’s taken me almost 14 days to switch over to burning fat not carbs, during which time I felt so rough, I’m actually too scared to go near a carb. But, seriously, why do you need to reload if you’re not using glycogen in the first place? I’m doing just fine, Crossfitting 4 times a week, in full ketosis, not a carb in site! And now I’m fully keto-adapted I feel tremendous. I’m doing this for performance, not for fat loss. Female, 49, 120lbs.


  13. Awesome video, THANK YOU TIM! Now I finally have a (reasonably) bite-size and credible bit of info to send friends and family who think my diet is insane.

    I’ve been doing intermittent fasting that has me in ketosis for most of the day, with a 4-6 eating window. Like some others on here, I use Asprey’s Bulletproof Coffee with butter and MCT oil as a breakfast that doesn’t break the fast, but then eat SCD foods for two big meals in my eating window. I’m vegetarian, so that’s basically beans, eggs, and veggies. Another commenter mentioned the price of coffee beans for BP coffee: Asprey’s beans are supposedly free of mold toxins, and they DO make me perform better on Lumosity brain games than regular beans… but you could get the ketosis effects with regular coffee beans, grass-fed butter, and MCT oil for cheaper.

    For anyone interested in getting most of the benefits of ketosis without an extremely restrictive diet, intermittent fasting with buttered coffee in the morning has been a great middle ground for me.

    Like Peter Attia, I LOVE the way ketones make my brain work, I’m never hungry, and I have consistent energy throughout the day. I had more cravings during the day when I had 30g of protein within 30 minutes of waking following strict SCD. Plus, now I can do sprints, lift weights, or do KB swings while fasting, just running on glycogen and ketones.


  14. Hello Tim and support team.

    My question is pretty straight forward, can I take PAGG during the CKD. I competed in Bodybuilding for years and I knew the late Dan Duchaine and have read his book. With the CKD. do you differ on the Carb loading phase. Lastly, what do you think of Garcinia Cambogia. I tend to use supplements that have stood the test of time, but I made an exception with Garcinia because of the claims that have been made. If the claims are true, would you recommend taking it during CKD?


  15. Got some new insights, thanks a lot! I made the experience that “playing” with carbohydrates’ share in my nutrition has an immediate effect on well being, performance and body fat. “All or nothing” doesn’t apply. Whether it is shape, performance or health – there’s nothing else to do but to try and error to find out the best long term carb – equilibrium to support the personal goals.


  16. Ketogenic diet worked for me very well but I didn’t strictly keep the 12-18 hours time after the glycogen depletion. Maybe it didn’t work that well, but it’s still a pretty fast weight loss plan. Especially when you train a lot


  17. Hi. I love the fourhourbody-diet. I feel really well in every aspect besides having palpitations. I have read about this and it seems many who start this diets gets them. I never had those in my life before so it must relate to the diet, and it seems that many gets them. Of course this is a matter for a doctor. But since so many experience the same problems could you give your opinion on the matter? It worries me a lot. I would love to continue eating like this for a long time since I like it, but palpitations are kind of scary…. Best, Anna


  18. I’m a bit of a latecomer to this post. I did ketosis for a couple months when I couldn’t go to the gym after a surgery. Some observations:

    * There’s a definite adaption period. You feel better 1-2 weeks in.
    * Once I was keto-adapted, it became my new “state”. If I had a bunch of carbs, I re-entered ketosis much more easily (as measured by ketostix)
    * Electrolyte balance was more difficult. I was occasionally lightheaded and had to pay conscious attention to salts. I probably should have eaten more avocado
    * Energy was pretty constant. Hunger far less pressing than on a regular diet, could go long stretches without food (and I’m already used to intermittent fasting)
    * I have IBS-like symptoms, which makes ketosis more difficult. Certain carbs, such as blueberries, seem to work miracles for my gut. On ketosis I had no idea how to fix things if digestion went awry.
    * When I went back to the gym (barbells), I experienced a crash. I went back to my usual carbs post workout diet. If I were sticking with ketosis, I’d have to pay much more attention to how to manage carbs
    * Intermitten fasting appears to have helped with keto-adaptation. I only took a few days to enter it the first time.

    Overall, a very useful diet for certain purposes. I was already lean, so no real weight loss need, but it would be very useful for anyone trying to lose fat. No hunger or cravings once you’re on it.

    Also an excellent option if for some reason you can’t do heavy lifting for a period (injury, traveling). Likewise great if you have to keep an irregular schedule.


  19. Keto was the best 3 weeks I ever had. I felt more energetic, alert, and stronger than before. I dropped 16 lbs while still gaining strength.

    It’s an incredibly difficult routine to follow. My favorite part was I could eat hot wings on a diet. How cool is that?


  20. It may be a bit difficult in terms drastically limiting your carbohydrate intake and find those types of foods you can enjoy. However, I think the benefits are much more extensive compared to the restrictions.

    It is difficult because it pushes into finding those types of foods which fit in with the ketogenic diet. And since most of the supermarkets are carbohydrate predominant, this is where it becomes challenging.

    Nevertheless, I found that dark-chocolate with 85% cocoa has only 3-4grams of net carbohydrates per 100grams (3.5oz), which means feast!


  21. Hi- I love your blogs and your podcasts. The question I have is “how long will I feel absolutely awful while exercising, after going into ketosis?” I initially only dropped my carbohydrate intake to about 125 grams per day. I did that for 3 weeks, then after reading and learning more, I dropped it to under 50 grams per day. During the 3 weeks of “moderate” carbs, I noticed that I was starting to struggle with workouts over an hour. At about mile 7 or 8 of a 12 mile run, I would feel like it turned into a death march. I tried increasing my carb intake a little (in the form of more fruit) for the day prior to a long run or in a meal 3 hours before. I still bonked at the hour point. Now that I have dropped to under 50 grams, I am not sure I could even run a mile. Do you have any encouragement or words of advice? If this will pass in a couple of weeks, I can tolerate it. Otherwise I will probably like to go back to adding a few carbs immediately before and during exercise.


    • hi,

      Not exactly sure of where you’re at in your timeline, but based on what I have read, eating 125 g of carbs per day is 20% of your daily carb intake (I assumed 2500 calories per day, which is 700 calories more than the average American woman, since you are an athlete), which perhaps isn’t low enough to fully keto-adapt. Also, 3 weeks might not be long enough to fully keto-adapt. So perhaps stick with your 50 g carbs/ day for another 3-4 weeks and then see how you feel.


    • Hey Kathy,

      the treshold is not necessary 50g of carbs per day, it’s individual. For some it’s above, for many people below 50g. As a general guideline I’d say the more metabolicly broken and insulin resistant someone is, the higher the carb intolerance and the lower the carbs have to be, in order to adapt.
      Personally, I kept them around 15g until it worked, just to be sure.
      Fat should be high (80% of the total kcal), protein moderate.

      The time it takes to adapt is individual as well. Too high protein, cardio training and other physical or mental stress can prevent keto-adaption. HIT in the first days of adaption-process might speed up the adaption. To soften adaption symptoms salt might help.
      Also while not yet keto-adapted and still in keto-flu MCT-oil or coconut oil (60% MCTs) do help most people, since MCTs can be used as fuel even though the body is not keto-adapted (yet).

      Good luck!


      • HIT is great for depleting glycogen quickly which forces your body to start burning fat. Be careful with keeping it going during ketosis though.

        You need a little bit of carbs to support mucous production, which in addition to the obvious places also helps form the lining in your gut. If you do lots of HIT in ketosis over more than a couple days and don’t re-feed with carbs, watch out for dry eyes and nose. If you keep going, dry gut > leaky gut > inflammation and new food allergies. I’m not sure I’ve given myself new allergies, but I did have dry eyes and nose with a sudden, unexplained weight gain and acne. Likely a bit of leaky gut and associated inflammation.

        From what I’ve read and experienced fat metabolism can support athletic efforts up to 80% of max. Sugar/glycogen is pretty necessary for higher efforts.


  22. I’ve just started with the high fat low carb diet, and logging all my foods in “My Fitness Pal” to keep track of my ratios of F/P/C. I’m having trouble keeping the carb percentage below 20%. I eat no processed foods, dairy, breads or gluten. My diet consists of lean meats, avacado, coconut oil, fresh vegetables and fruit. Water and unsweet tea are my only drinks. How do I keep the carbs lower?


    • Jake, I also use the MyFitnessPal to keep track of my food and one think that you should be aware of is that the 20% carbs is gross and doesnt subtract the fiber amount which is what you are suppose to do. Like avocados have carbs but they get cancelled out but the high amount of fiber so the net result is very low. I suggest you take that into consideration because you might still be at a very low net carb count. I would also limit fruit to once a week and smaller portions as the geneticly modified fruit we have today is about 200% bigger then what it used to be . Strabberies are the size of apples now and apples the size of watermelons! ..and watermelons well you might need a friend and a truck to take one home. ;lol :) Good luck!