Ketosis was the topic that sparked the most objections when I described it as the “promise land” in my low carb journey. Responses ranged from anywhere between “you were not in ketosis” to “6 week adaptation period is not enough” and in-between-the-lines “you are a pussy”. Mainly this is also my fault, as I didn’t described my experience with ketosis in greater extend. Therefore the topic merits another blog post from my side.
So for anyone not familiar to ketosis I would refer you to an excellent book The Art and Science of Low Carbohydrate Performance by Jeff Volek and Stephen Phinney or to (free) article by Phinney. Also, the entries for Ketogenic diet and Ketosis are fairly well written in Wikipedia.
The basic premise of the ketogenic approach to endurance training lies in the fact that by greatly reducing the amount of carbohydrates in diet the body is relying mostly on ketone bodies for muscle and brain fuel. Ketone bodies are produced from fatty acids, of which we have basically unlimited stores. Hence by not relying on glycogen stores for fuel, one could not experience the so feared bonking. When studying the topic in literature I was skeptical at first, but decided to give it a try nonetheless. The issue that bothered me the most was, why isn’t this approach more popular, if the benefits are quite substantial, as described in famous study by Phinney et al. Also, Peter Attia reported some favorable results at his blog that additionally convinced me to try it out.
So with good hopes and armed with blood ketone meter (and that expensive testing strips!) I reduced my carbs to under 50 g per day and protein to about 120 g per day. Over the 6 week period I had average morning blood values of ketones around 1,2 – 1,5 mmol/L. (That goes for the first argument “you were not in ketosis”). I was in ketosis all right, but I was feeling miserable as hell. No motivation to train, always cold, difficulties to start even basic movements like going to the bathroom, and I had traumas before swimming sessions as I was freezing in the water! It was MISERY in capital letters. Especially because my performance dropped like a piece of stone to the bottom of the pool. Sure, I wasn’t fading on long workouts, but the power and pace were very low. Also in interval work or hill repeats I couldn’t find that extra low gear for maximum effort. It’s really hard to describe, as I know that I would not believe myself explaining it to me, if I wouldn’t have tried it! It just didn’t work for me and my style of training which involves quite a bit of interval training sessions per week. My body was basically starving, although I was consuming in the range of 6000 kCal per day. I’ve lost quite a bit of muscle and gained back some fat mass, because I misinterpreted my cravings for carbs with cravings for food.
This brings me to the comments like to “6 week adaptation period is not enough” and “you are a pussy for not sticking to it”. My reply would be, that 6 weeks in that state and training on average 3 hours per day, with approx. 5-6 interval training sessions per week, seemed like eternity! And I believe that 3 years of 2-3 hours per day endurance training raised my self-discipline and pain threshold to a level, that cannot be offset very easily.
Anyway, after trying the ketosis and observing the effects, I would now line with the opinion by Robb Wolf that he nicely conveys on his blog in 3 parts (part 1, part 2, part 3). Or if you want a more colorful and juicy read head over to Anthony Colpo’s blog for his thoughts (part 1, part 2).
So to summarize, I believe that ketosis, being an evolutionary feature that enabled us to survive the periods of famine, is not a good approach to enhance endurance training, if that training (or racing) requires any significant higher intensity periods. Long ultra-endurance events could be an exception, but for “normal” endurance events and for goals more ambitious as “just finishing”, I believe that ketosis isn’t optimal approach. The endurance training by itself is already stressful enough, so the additional cortisol release during ketosis might just have too many negative consequences (i.e. muscle wasting).
Also, one of the major motive to go into ketosis while training and / or racing is reliance only on endogenous stores of fuel (i.e. fat stores). I have now raced two Ironmans on “train low race high” carb approach and on both occasions I haven’t had a slightest issue with energy intake. Being fat adapted enabled me to efficiently burn fat in such extend, that I can easily manage the required carb intake during 9h event and still perform at quite high intensities (i.e. under 3 hour marathon on both Ironmans). In Hawaii 2013 I was consuming approx. 45 g of carbs per hour, which is almost half less of what I used to, when I wasn’t fat adapted (81 g per hour in Hawaii 2012). Hence, the required intake of carbs while being fat adapted is very manageable and will rarely cause problems also in athletes with troublesome stomach. Ketosis therefore looses another highly regarded feature, that was so alluring on the first sight. After experimenting with quantities, the arguments of “unlimited body fuel supply” and “unnecessary fuel intake during races” aren’t so appealing anymore when you also factor diminished performance into equation!
All in all, the ketosis experiment was very valuable experience for me. Having read most of the scientific literature on ketosis and endurance training, surfing through numerous blogs, podcast and videos I must say, that reading cannot prepare you for the experience. You just have to try it to really see what ketosis is like.
That being said, I still plan to use ketogenic nutrition periodically when I finish competing and return to “normal living”, as there have been suggestions on its beneficial effects on general wellbeing. Especially the idea of periodic intermittent fasting is appealing to me, as I think that we are more adapted to irregular meal timing. If the composition of the meals is appropriate, of course!