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!
Hi, I found your site by accident and would value your advice. I live in the UK and in 4 weeks will be cycling a very challenging route for “lejog” (Lands End to John O’Groats) which will be around 1200 miles, with 57,305 feet (17,467 KM) of climbing. Around 2 months ago, I began to look to see how I could fuel such a ride and (after reading everything I could find including “The Art and Science of Low Carbohydrate Performance” and “The Art and Science of Low Carbohydrate Living” also “Ketoclarity”) I decided Ketosis was for me. I am now trying to plan what food I will actually take. My understanding is on the hillier days I will be more in the red (thus burning more Glucose) – Note I have read the study suggesting otherwise but will assume I DO need to replenish my carb store en route – but am at a loss as to what Carbs to take. In the UK we do not have access to the superstarch often mentioned. Can you offer any advice? I have 1 day off in 7 (3 week planned route) so I worry I won’t have the chance to replenish my carbs. One thought was to take low GI carbs and consume every 20 miles or so (but I worry I’ll be kicked from Ketosis). I note you have cycled many 100+ mile endurance rides and any advice you can offer is very much appreciated. Regards, Chris