"It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong."—Richard P. Feynman
In the journal Metabolism (link to full-text).
"Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations....
"Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar."
The fat-burning rates and the lack of difference in glycogen consumption/replenishment are both game-changing findings. The glycogen findings are especially interesting, as they indicate that glycogen is being used for some purpose other than as fuel:
3.5. Muscle Glycogen
Compared to baseline, muscle glycogen was significantly decreased by 62% immediately post-exercise and 38% at 2 hours post-exercise in the HC group. The LC group exhibited a similar pattern; muscle glycogen was decreased by 66% immediately post-exercise and 34% at 2 hours post-exercise (Fig. 6A). There were no significant differences in pre-exercise or post-exercise glycogen concentrations between groups. There was a high degree of variability in muscle glycogen concentrations pre-exercise in both groups. In contrast, the depletion and resynthesis patterns showed a more uniform response, especially the amount of glycogen synthesized during the 2 hour recovery period in LC athletes (44.8 ± 7.5; 95% CI 40.2–49.4 μmol/g w.w.), which was one-third less variable than HC athletes (34.6 ± 23.9; 95% CI 19.8–49.4 μmol/g w.w.) (Fig. 6B). Interestingly, in all ten LC athletes the total amount of carbohydrate oxidized during the 3 hour run as calculated from indirect calorimetry (mean ± SD; 64 ± 25 g) was lower than the total amount of glycogen disappearance (mean ± SD; 168 ± 65 g), assuming 10 kg of active tissue.
So a low-carb diet means less variation in glycogen repletion, and no impact on glycogen levels or replenishment!
That sound you hear is the dietary recommendations for athletes being shattered...
Vespa, the company that
apparently helped Phinney & Volek find the keto athletes involved, has a post here including the names of some of the athletes.
P.S. Not "apparently":
P.S. Not "apparently":
"The authors would like to thank Peter Defty for assistance in recruiting participants and the extraordinary research participants for their enthusiasm to participate in this project."