Intermittent Exogenous Ketosis for Athletic Performance, Recovery, and Adaptation

Abstract

Abstract Sports nutrition science seeks to determine optimal dietary protocols for athletes pushing the limits of human physiology in power, endurance, and skill. Traditionally, dietary interventions aimed to stimulate performance have focused on strategic intake of carbohydrates, protein, and fat. However, recent development of oral ketone supplements has increased the popularity of intermitted exogenous ketosis (IEK) as a potential nutritional strategy to stimulate training adaptation and performance in athletes. Several physiologic mechanisms are implicated in acute modulation of exercise performance by IEK. These include use of ketone bodies as an alternative substrate for oxidative ATP production in contracting muscles and ketone-mediated inhibition of glycolytic flux. The latter could lead to glycogen sparing, which may increase endurance; on the other hand, glycolytic inhibition in conjunction with ketoacidosis could be ergolytic in short maximal exercise bouts. Furthermore, preliminary evidence suggests that acute and chronic post-exercise ketosis may stimulate recovery from training. Acute IEK could stimulate muscle protein synthesis and glycogen repletion, and chronic ketone ester intake blunted overreaching symptoms during short-term endurance training overload. This protection could be attributed to improved autonomic neural balance, appetite and stress hormone regulation, and possibly attenuation of exercise-induced inflammation and oxidative stress. Such effects could conceivably either down- or upregulate training adaptation. However, research to date describing both acute and chronic exogenous ketosis in exercise and training is limited and inconclusive. Further studies are required to elucidate the specific contexts and mechanisms whereby IEK could maximally benefit athletes.