Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes

Fionn T. McSwiney, Bruce Wardrop, Parker N. Hyde, Richard A. Lafountain, Jeff S. Volek, Lorna Doyle

Research output: Contribution to journalArticlepeer-review

133 Citations (Scopus)


Background Low-carbohydrate diets have recently grown in popularity among endurance athletes, yet little is known about the long-term (> 4 wk) performance implications of consuming a low-carbohydrate high fat ketogenic diet (LCKD) in well-trained athletes. Methods Twenty male endurance-trained athletes (age 33 ± 11 y, body mass 80 ± 11 kg; BMI 24.7 ± 3.1 kg/m2) who habitually consumed a carbohydrate-based diet, self-selected into a high-carbohydrate (HC) group (n = 11, %carbohydrate:protein:fat = 65:14:20), or a LCKD group (n = 9, 6:17:77). Both groups performed the same training intervention (endurance, strength and high intensity interval training (HIIT)). Prior to and following successful completion of 12-weeks of diet and training, participants had their body composition assessed, and completed a 100 km time trial (TT), six second (SS) sprint, and a critical power test (CPT). During post-intervention testing the HC group consumed 30–60 g/h carbohydrate, whereas the LCKD group consumed water, and electrolytes. Results The LCKD group experienced a significantly greater decrease in body mass (HC − 0.8 kg, LCKD − 5.9 kg; P = 0.006, effect size (ES): 0.338) and percentage body fat percentage (HC − 0.7%, LCKD − 5.2%; P = 0.008, ES: 0.346). Fasting serum beta-hydroxybutyrate (βHB) significantly increased from 0.1 at baseline to 0.5 mmol/L in the LCKD group (P = 0.011, ES: 0.403) in week 12. There was no significant change in performance of the 100 km TT between groups (HC − 1.13 min·s, LCKD − 4.07 min·s, P = 0.057, ES: 0.196). SS sprint peak power increased by 0.8 watts per kilogram bodyweight (w/kg) in the LCKD group, versus a − 0.1 w/kg reduction in the HC group (P = 0.025, ES: 0.263). CPT peak power decreased by − 0.7 w/kg in the HC group, and increased by 1.4 w/kg in the LCKD group (P = 0.047, ES: 0.212). Fat oxidation in the LCKD group was significantly greater throughout the 100 km TT. Conclusions Compared to a HC comparison group, a 12-week period of keto-adaptation and exercise training, enhanced body composition, fat oxidation during exercise, and specific measures of performance relevant to competitive endurance athletes.

Original languageEnglish
Pages (from-to)25-34
Number of pages10
JournalMetabolism: Clinical and Experimental
Publication statusPublished - Apr 2018


  • Body composition
  • Endurance
  • High-carbohydrate
  • Ketogenic
  • Performance


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