Very Low Carb Diet May Impair Athletic Performance

Very low carbohydrate “keto” diets can increase oxygen uptake (VO2 peak). However, this doesn’t necessarily translate to an improvement in athletic performance, and may be detrimental. In this study of 21 race walkers, researchers assigned them to a very low carb “keto” diet, or 2 different types of high carb diets. In the keto diet, the participants experienced reduced economy, meaning their bodies required more oxygen at a given speed, despite their increased VO2 peak. This translated to no improvement in the keto diet group speed, with 5.3-6.6% improvements in speed for the high carb diet groups.
The Journal of Physiology. 2017 May 1;595(9):2785-2807. doi:10.1113/JP273230. (Burke LM et al.)