I did not start a ketogenic diet to improve athletic performance. I started it to protect my brain from dementia.
I agonized for months over how it would affect my training on the bike. I worked through it and have been sharing for months now how my performance has improved. I suspected it had a lot to do with my diet, but thanks to a recent study, I have proof that it is definitely in large part due to my ketogenic diet!
The study discussed a clinical trial conducted in part by 2 familiar names in the low carb world, Jeff S. Volek and Stephen D. Phinney. 20 elite ultra-marathoners and ironman distance triathletes participated in the clinical trial, and were studied to determine the extent of metabolic adaptations. The results were surprising to some: Long-term keto-adaptation results in “extraordinarily high rates of fat oxidation.” The study also found that there was no higher rate of muscle glycogen depletion in the low carb athletes – rather the muscle glycogen utilization and repletion patterns before, during and after a 3 hour run by the participants were similar.
Dave Asprey wrote on Bulletproofexec Blog about this study and it is an excellent read. He explains what the prior concerns about a low carb diet were as it pertains to performance – past studies concluded an athlete would “top out” at 10% of energy provided from fat and the rest would have to come from glucose stored in your liver and muscles. The belief was that if you followed a low carb diet and could only access 10% of your fat for energy, then you would end up breaking down muscles for energy (where glucose is stored). Others believed you could harm your liver by depleting it of glycogen while following a low carb, high fat diet while engaging in intense physical workouts.
Both Jonathan and I have worried about glycogen depletion and have used products like UCAN’s SuperStarch to try and avoid that. I’ll need to digest this study a little more, but at first read the results seem be telling us we don’t need to worry about glycogen depletion. Definitely good news for us and other endurance athletes!