Keto/Carnivore Diets and Endurance Exercise Performance: Part 2

What happens when real athletes go keto?

In Part 1, we examined two studies involving athletes that allegedly demonstrated positive results for ketogenic diets. Except they didn’t.

Both studies, which just happened to involve keto diet book authors, did not show tangible performance improvements. The infamous Phinney study showed marked performance declines in 2 of 5 cyclists following a keto diet, and no change in another. The improved time to exhaustion of the remaining 2 cyclists was an artifact, not of diet, but of the highly flawed study’s lack of a routine familiarization procedure.

The other study, by McSwiney et al, showed reductions in absolute power and relative power per kg of lean mass in the keto group.

These negative findings were obtained in the lab setting, while the athletes rode stationary bicycles. In their real world training, the athletes reported temporary energy crashes and a sustained worsening of their ability to perform at higher VO2max levels (for example, reduced sprinting performance).

Low-carb authors, most of whom are sedentary creatures that do not engage in high-level training, insist keto diets are fine for athletes. They casually brush off the retarded endurance performance at higher intensities as but a minor flaw, when in reality it could quite literally mean the difference between first and last place.

In their book, The Art and Science of Low Carbohydrate Performance, Volek and Phinney claim “if humans are given two or more weeks to adapt to a well-formulated low carbohydrate diet, they can deliver equal or better endurance performance compared to the best high carbohydrate diet strategy.” (Bold emphasis added)

That’s complete nonsense.

In this post, we’ll look at some real life case studies and more clinical trials that underscore why athletes should avoid ketogenic diets wherever possible.