Effect of a four-week isocaloric ketogenic diet on physical performance in very high-altitude: a pilot study

Abstract Background: Ketogenic diet (KD) reduces carbohydrate (CHO) daily ingestion replacing majority of calories by fat. KD is of increasing interest among athletes for evidence about VO2max increment. This is the principal performance limitation in high altitude. We so examine the tolerance of a 4-week isocaloric ketogenic diet (ICKD) under simulated hypoxia, the possibility of evaluating participant’s ICKD performances benefit by a maximal graded exercise bike test in hypoxic condition and assess data on its effect on performance markers and arterial blood gases.Methods: Using a randomised single blind cross-over model, 6 recreational mountaineers (24 to 44 years) completed a 4-week ICKD either followed or preceded by a 4-week habitual mixed western diet (HD). Performance parameters (VO2max, lactate threshold (LT), peak power (Ppeak)) and arterial blood gases (PaO2, PaCO2, pH, HCO3-) were measured at baseline under two conditions (normoxia and hypoxia) as well as post 4-week HD and post 4-week ICKD under hypoxic condition.Results: We analysed data of 6 participants. Hypoxia led to a decreased performance in all participants. ICKD diet decreased their PaO2 by -14.5% and increased their VO2max by +7.3% and Ppeak by +4.7%.Conclusion: All participants except one could complete the ICKD. VO2max improved with ICKD under the hypoxia condition. ICKD is thus an interesting alternative to CHO dependency for endurance performances at high-altitude (1500-3500 m) including high-altitude training sessions and high-altitude races. Nevertheless, the PaO2 decrement with ICKD remains a significant limitation of ICKD in very high- to extreme-altitude (>3500 m.). Trial registration: CER-VD, 2020-00427. Registered 18.08.2020 - Prospectively registered