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

Nicolas Chiarello; Bertrand Leger; Mathieu De Riedmatten; Michel F Rossier; Philippe Vuistiner; Michael Duc; Arnaud Rapillard; Lara Allet

doi:10.1186/s13102-023-00649-9

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

BMC Sports Sci Med Rehabil. 2023 Mar 20;15(1):37. doi: 10.1186/s13102-023-00649-9.

Authors

Nicolas Chiarello¹, Bertrand Leger², Mathieu De Riedmatten³, Michel F Rossier^{4

5}, Philippe Vuistiner⁶, Michael Duc⁷, Arnaud Rapillard⁷, Lara Allet^{5

8}

Affiliations

¹ Department of Medicine, University Hospitals of Geneva, University of Geneva, Geneva, Switzerland. Nicolas.chiarello@outlook.com.
² Clinique romande de réadaptation, Sion, Switzerland.
³ Emergency Department, Hospital Valais/Wallis, Valais, Switzerland.
⁴ Service of Clinical Chemistry and Toxicology, Central Institute of the Hospitals - HVS, Sion, Switzerland.
⁵ Department of Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland.
⁶ Institute for Research in Rehabilitation, Clinique romande de réadaptation, Sion, Switzerland.
⁷ Swiss Olympic Medical Center, Clinique romande de réadaptation, Sion, Switzerland.
⁸ Valais-Wallis School of Health Sciences, HES-SO, University of Applied Sciences and Arts Western Switzerland, Valais, Switzerland.

Abstract

Background: A ketogenic diet (KD) reduces daily carbohydrates (CHOs) ingestion by replacing most calories with fat. KD is of increasing interest among athletes because it may increase their maximal oxygen uptake (VO₂max), the principal performance limitation at high-altitudes (1500-3500 m). We examined the tolerance of a 4-week isocaloric KD (ICKD) under simulated hypoxia and the possibility of evaluating ICKD performance benefits with a maximal graded exercise bike test under hypoxia and collected data on the effect of the diet on performance markers and arterial blood gases.

Methods: In a randomised single-blind cross-over model, 6 recreational mountaineers (age 24-44 years) completed a 4-week ICKD followed or preceded by a 4-week usual mixed Western-style diet (UD). Performance parameters (VO₂max, lactate threshold [LT], peak power [P_peak]) and arterial blood gases (PaO₂, PaCO₂, pH, HCO₃^-) were measured at baseline under two conditions (normoxia and hypoxia) as well as after a 4-week UD and 4-week ICKD under the hypoxic condition.

Results: We analysed data for all 6 participants (BMI 19.9-24.6 kg m^-2). Mean VO₂max in the normoxic condition was 44.6 ml kg^-1 min^-1. Hypoxia led to decreased performance in all participants. With the ICKD diet, median values for PaO₂ decreased by - 14.5% and VO₂max by + 7.3% and P_peak by + 4.7%.

Conclusion: All participants except one could complete the ICKD. VO₂max improved with the ICKD under the hypoxia condition. Therefore, an ICKD is an interesting alternative to CHOs dependency for endurance performance at high-altitudes, including high-altitude training and high-altitude races. Nevertheless, decreased PaO₂ with ICKD remains a significant limitation in very-high to extreme altitudes (> 3500 m). Trial registration Clinical trial registration Nr. NCT05603689 (Clinicaltrials.gov). Ethics approval CER-VD, trial Nr. 2020-00427, registered 18.08.2020-prospectively registered.

Keywords: Endurance exercise; High-altitude; Hypoxia; Ketogenic diet; Low-carbohydrate; VO2max.

Associated data

ClinicalTrials.gov/NCT05603689