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.

Watch The Tim Ferriss Experiment, the new #1-rated TV show with "the world's best human guinea pig" (Newsweek), Tim Ferriss. It's Mythbusters meets Jackass. Shot and edited by the Emmy-award winning team behind Anthony Bourdain's No Reservations and Parts Unknown. Here's the trailer.

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

  1. I did Kiefer’s Carb Nite protocol for six months last year. I’m 50 lbs overweight, and have been Crossfitting for almost three years. Down 50 lbs from pre-Crossfit days and figured I’d try Carb Nite after seeing Mark Bell’s results from 2012. The problem with ketogenesis and Crossfit is maintaining energy levels that support metcon performance. Some days in the gym were fine, but others were horrible in terms of strength and energy. If I do Carb Nite again I’ll take six months off from metcons and take on more of a strength-only focus. I lost 20 lbs on Carb Nite but once I returned to eating carbs regularly 10 lbs came right back. No big deal though…so did my performance in the gym. Might try carb nite with two refeeds during the week (exclusively rice & sweet potatoes) to maintain glycogen levels.


    • I find 2 carb nites a week work the best. Especially when doing crossfit style workouts. Usually my carb nites are rice dishes. I love rice.


      • I’m currently also following CarbNite, currently at 9% BF at 210lb, 6′. It’s a solid program, and hits the reward/sacrifice schedule with the yummy carb re-feeds. I keep the ULC days paleo, and the carb re-feeds GF. Lift 5 days a week (shockwave) 2 days of HIIT post re-feed, working great! feel awesome


      • To put my comment in context, I only know Kiefer through his direct work with the Supertraining Gym team and athletes like Mark Bell. He and I have spoken in person a few times, and his results with powerlifters have been impressive. I am not very familiar with his writing.


      • Perhaps, but he has been exposed multiple times for citation abusing – nicotine, creatine, the running article I mentioned, etc etc.

        It’s systematic and a gross appeal to “look at all my citations.”


      • Kiefer has a background in physics not physiology. This much is obvious from the free chapters of CarbNite available on his site.

        At PaleoFX he actually claimed that women metabolize carbs differently than men and shouldn’t even have them after a workout. Oh and don’t run bitches cuz it will give you a flat ass. Hardcore Dangerous Kiefer :-)


      • Tim Sol has an excellent guide at all things supplements, check it out at www. examine DOT COM.
        He knows his stuff.


  2. I’ve messed with extremely low carb all week, refeed post workout saturday, 11am until 8pm-ish. Ive also tried adding a carb night on wed (100g of carbs for dinner). Havent had great success with either. My goal is to always be under 7-8% BF.
    I do a lot of olympic lifting and hypertrophy after, 5 days a week. All of my carbs come from, white rice, sweet potatoes, a little fruit (berries).
    So my question is, what am I doing wrong?

    Thanks Tim


    • You have tried for 1 week, and you ask what you are doing wrong? Give it a go for a longer period a month or two. White rice, You don’t know about insulin, or Tim’s and most people in general trying to drop weight. Don’t eat anything (carbs) that are white. I don’t know you, but you say you do Olympic lifting followed by Hypertrophy ( training I assume ). After Olympic lifting then training to build muscle after (same day?). That is Ridiculous. There is not enough time (are you in a ketogenic state/ 1 week), and the amount of information you give, nobody could tell you what you’re doing wrong…. Just to kindly point that out.


  3. I tend to aim for a protein filled dinner and intermittent fast until 2pm next day, which is sufficient to reach a state of ketosis (as checked by ketostix). Coupled with a work out c. 12 hours post last meal, it really kicks off ketones in the body! Have been using this technique for fat loss post a heavy weekend of eating/ drinking, but clearly not daily. 1-2 days of that shows strong results on fat stores for me.


  4. I am in ketosis now!!! I go between a 4hr body and a strict Keto diet depending on my mood and how bored I get with the keto. The one thing that makes it easy to keep going is using ketostix to see if I am in ketosis, that and losing weight of course. I am less likely to break my diet or even come close to cheating if I am in a dark maroon zone of the stix and when I am not I tend to diet harder to get there. I have lost 27lbs in three months and that is with 8 days of hardcore cheating in Hawaii where i put back on 7lbs that I had lost. They came off pretty fast when I got back into the swing of things of course. I am shooting for another 20-30lbs. Thank you for your book, you put me on the right path.


  5. I’ve done Keto for the last four months. I love it. Went from 198 lbs to 178 lbs and feel like I’ve added a little muscle doing a lot of compound movement weight lifting.

    I’ve followed a simple Keto diet most of the time, keeping carbs to 5%, protein 20%, and fats around 70%. Tried a cyclical keto for a few weekends but wasn’t disciplined enough not to have fats with carbs.

    I started reading Peter Attia’s website,, a month ago. The guy is like Keto Superman. So much great information from a very reputable source, not only with medical knowledge, but athletic application data.

    Definitely recommend following a Keto diet if looking to drop fat.


  6. After watching Dr. Attia’s TED Med talk and checking out his website, I tweaked my Paleo diet to incorporate some dairy. It hasn’t hurt my fat loss and has given me more options. I enjoy ketosis; I have a clearer head, more energy, less food cravings, and I am losing a couple of pounds a week without any real training.


  7. Hi Tim,

    I first experimented with ketosis after reading 4HB nearly one year ago. I lost about 8,5 kg in 8 weeks but I probably gained 2 kg of muscle in that time too. I still live on the slow carb diet since then with influences of John Romaniello´s advices of intermittent fasting and Dave Asprey´s Bulletproof Coffee which is my breakfast. I am feeling very well and I am on track to reach my phsyical goals. I recommended the slow carb diet to a colleague of mine who lost 10 kg of fat in 5 weeks – she loves me now ;-) – thanks to you! The only con of being ketonic – bad breath. But if you know it you can work against it.

    Thx and all the best!


  8. I prefer to be in ketosis most of the time. I prefer it because I have more consistent energy and don’t feel as hungry as often. Also, as long as I’m eating grass fed meat, pastured eggs, organic bacon, ect. I find that I can eat like a fatty and stay at around 12% bodyfat, andI don’t just have a “fast metabolism”, i use to weight 300lbs. Only con for me is that I have to piss every hour while in ketosis.


  9. I have found using blood ketone monitors are a much more accurate way of measuring ketones than urine sticks, very easy to do too!
    An interesting read is ‘The Art & Science of Low Carb’ Performance’

    Dave Asprey also has really interesting views on exercise & ketosis in this video interview here

    Awesome topic!!! And thanks for sharing Tim… Guy


    • The Dave Asprey link is a great resource filled with lots of useful bits of information. Just listened to the whole interview while on my morning run and was inspired.

      Thanks for this


  10. I’ve tried no-cabohydrate before and just felt really horrible, I.e. massive headaches, complete exhaustion, hunger, depression, haziness. I’m considering increasing portion sizes and waiting it out, to see if it improves but generally I’m actually kinda confused about diet these days. Everyone has their own idea about what’s right and the data is often misleading.

    Right now I’m on the slow carb diet but adding in some sweet potato, I’ve been losing weight, but put on a bit too much weight on cheat day that doesn’t go away fast enough. I have made progress, on my 2nd month, gonna go for another 30 days, maybe cut out the sweet potato, maybe include come no-carb meals but generally been finding the whole dieting thing confusing and frustrating. I find I get extremely hungry and kind exhausted and sick at night also.

    I’m sure people here will be pro SCD generally but any advice on how to clear up the fog and confusion on diet (could just be my own brain-fog) would be greatly appreciated, thanks.


    • Alex, I have tried and failed at low carb diets several times and I think I’ve figured out how to make them manageable. I first tried slow carb and paleo with dismal results. It wasn’t that they were too strict. On the contrary: They weren’t strict enough. Also I just found out I am hypothyroid, so beans are some of the worst foods I can eat. Had no idea…

      Apart from not feeling well if you are experiencing fat loss, I’d continue to tweak the diet. Tim lists the common mistakes people make in the 4HB. I was frustrated when it wasn’t working for me, but as it turns out it was the beans. The number 1 mistake with low carb diets is not eating enough. Another is exercising too much. Not drinking enough water. Eat very generous portions. Someone I just had dinner with looked at me like I was committing slow suicide when I had 2 bun-less Double Doubles (no cheese) from In-N-Out burger for dinner tonight. Sure enough the ketostix say I have a “moderate” amount of ketones in my system, which is great compared to none, which is what I had a few days ago. In particular, eat more fat. It will help with energy and satiety. It has for me. Good luck.


      • Best keto meal is a 4×4 from in n out, protein style and mustard-fried. 56g fat 60g protein and only 3g carbs.


  11. Mostly utter nonsense;

    1. N=1 experiments mean NOTHING.
    2. NUSi has more inherent bias than any medical journal ever could.
    3. There is no difference in fat loss between low carb keto and low carb non-keto diets.
    4. Lyle would go bugsh*t if he found his name alongside Kiefers. And would probably lose his sh*t if he knew how much his work has been bastardized here.
    5. 5 words: Metabolic ward studies – see them.


    • I’m not claiming Lyle’s work is reflected in anything in this post. I’m trying to give credit where credit is due for piquing my interested in ketogenic diets, generally speaking.


    • You need to go to Attia’s blog and read it. I paid the $50.00 for Lyles book and it’s amazing but Attia takes it to a new level – and so he should it’s ten years plus after Lyle’s publication.


    • Who cares if “Lyle would lose his shit” or not. Let him do that and spread his childish, arrogant antics on even more message boards, so more people can be exposed to his questionable character.

      In fact, why don’t you direct him to this blog post, I’m sure it would rile him up good.

      Thanks for posting the video Tim, I’ll brew a pot of Maté and watch it before bed ;-)


  12. Ive been on a 60 day test of MCT oil supplementation. I stopped all coconut oil intake. Resumed animal fat [butter intake]. I de-loaded my training for the period, did only 5 metcons, no lifting, but than maintained my normal regimen of surfing. I 90% paleo , and tried not create a fair base line, and try to get my body into ketosis. Very low carb intake which I actually bummed up especially prior of Intermittent Fasting. Been feeling over trained so Ive been using carbs to promote a food coma and get to sleep. Its helped. Were talking a small portion of white rice or corn flakes. I followed Nate Miyakis recommended approach here

    5 days on 2 off. 5000mgs a day was the regimen

    I gone from 223lbs to 212. Per skin fold test Im 8.06 [21 pinch, 7 site test] and from the same person I was 10.24

    Only thing I bumped up was hydration after review I not hydrating enough.

    Side effects, have been a curious heart flutter which at first was weird. After some looking into it it is a small but obvious side effect.

    I anticipate blood work soon to assess lipid panel and triglyceride levels. I get most of my panel see if there are any weird correlates from the MCT’s.


    • Palpitations are fairly common when first entering a ketogenic state. This goes away for most people fairly quickly. I had this problem initially as well.


  13. This is awesome Tim! Are you still on the SCD or do you switch around? I’m a big fan of SCD + KB training…really good way to look good with minimal time investment. What kind of workouts and diet are you currently doing?


  14. I’ve experimented with one before and concluded it a losing proposition when competing in athletics (demanding anyways), mainly because you will require CHOs if using a mix of power and endurance modalities. If a sport required less dynamics, a more steady-state, then I can see how a ketogenic approach may be undertaken. To me, it would depend on the quality and quantity of all-out efforts required by your undertaking. On a side note, one thing that gets lost in the macronutrient wars is food reward theory. Instead of thinking about diets from a typical macro-perspective, it is important begin to understand the organ that probably mediates all diets effects, the brain. I experimented with keto-dieting when “revisiting” competitive tennis (an ex-college player) and I feel it limited my efforts in significant ways.


  15. Ketosis has worked very well for fat loss, better than slow carb but harder to sustain. My body seems to sustain on slow carb not lose, but ketosis definitely gets the needle to move.

    Thanks for posting this resource, and for all the excellent discussion that’s bound to follow.


  16. With true ketosis, you can’t really even eat protein, because your body will fight ketosis *so* hard that it will take all available protein and convert it desperately into carbs.

    If you really want to box your body into a metabolic corner, then sure, go for ketosis, but you’re really limited to eating just fat. Otherwise, you’ll pop right out of ketosis.

    A high protein diet without carbs is essentially still a high carbohydrate diet, it’s just going to put a ton of stress on your liver in the process.

    And, think about this: If you don’t eat anything, what are you living on after your glycogen stores are depleted? You’re living on *yourself* when you are starving, and you are made of protein, and fat.

    So if you *eat* only protein and fat, aren’t you just “simulating” starvation, on a metabolic level?

    Ketosis is a fad unless you’ve got a real medical reason to use it, it’s probably a good idea to not mess with your metabolic function to that level. You’ll probably be kicking yourself in a few years when you start wondering why you can’t eat carbs, or higher calories anymore without packing on fat.


    • Have you done keto?

      You *can* eat protein on keto, as long as you stay within your personal needs. It is not a fad, and it works for some people (I’m not saying that it will work for anybody).

      Also, some people might have better results by doing any other diet.

      It works for me, and a lot other people. Look up /r/ketogains and /r/keto in reddit for lots of success stories. ;)


      • FWIW the science isn’t settled on this either – AFAIK. The accepted dogma is that GNG drives blood sugar up with excess protein, but mostly it’s extrapolation of noticing that blood sugar rises on a meal of protein. Especially in the arena of ketosis which is even less researched, GNG on anything but an infintessimal scale doesn’t seem logical – if there’s enough fat available (which produces glycerol and ketones as a by-product) then the reason for the body to use a very metabolically expensive process to rip apart structural proteins for it’s glucose seems absent.

        Very few people question it – even fewer studies and journals – it’s just accepted that GNG is the fate of “excess” protein, but we’re relying on a theory mostly:



        This blog post includes a graphic of all the places different amino acids can feed into the Kreb’s cycle, etc.

        There is no evidence that gluconeogenesis is substrate driven, and it is certainly false that excess protein must be converted to glucose to be used for energy (or stored as fat).

        Also some AA are ketogenic, notably the BCAA’s. Dairy and beef would be good choices for protein sources then …


    • You obviously don’t know what you’re talking about. I consume 100-150 grams of protein and about 30 grams of carbs a day but still remain in ketosis with little to no exercise. I don’t use ketostix. I test via blood using the Precision Xtra 2x a day.


    • There must be something off in your assumptions, because for the past few years I have typically eaten < 30 g of digestible carbohydrates (i.e. not including fiber) per day and my strength is not all that bad, nor have my muscles atrophied to the extreme, as your analysis implies they should have.


    • The slow carb as described in 4HB does not lead to ketosis. Probably only 1 big serving of beans/lentils per day is enough carbs to keep you out.

      To dip into ketosis, your diet pretty much must consist only of meat and veggies – maybe with some nuts or something. Eat plenty of fat. Always buy organic.


  17. I’m a relatively competitive powerlifter and I’ve been training 4 times a week for the past 7 months pretty much always in ketosis and almost always semi-fasted. When I started in January I was 200lbs and I just competed in a powerlifting meet at 183lbs after a 2lbs water cut. I unfortunately didn’t take measurements but I’m almost certain I’ve gained some muscle while losing fat on this diet.

    The only problem that I have with ketosis is that I don’t sleep as well. Using my fitbit track my sleep efficiency is always below 50%. I’m wondering if anyone has any tips on improving sleep quality while on a ketogenic diet?


    • Some people fare well with Raw Honey in small amounts before bed. Also, some people have used Trehelose before bed as well. This is to give you body just enough glucose for the brain while sleeping. I don’t have personal experience with this but I can share sources of information on this. Also, many have tried non-denatured grass-fed whey protein concentrate, collagen protein, and/or mct oil before bed as well as certain peptides.

      Are you supplementing magnesium? Magnesium glycinate helps my sleep tremendously, as does cold thermogenesis. Also, sleeping in a completely pitch black room with limited EMFs nearby you, and possibly eliminating blue-light frequencies prior to bed (i.e. use blue light blockers, f.lux, and turn lights off unless using amber bulbs or candles).

      Hope this helps!