Kinesiologists at McMaster University have found ketone supplements, used by some athletes hoping to cross the finish line faster, may in fact worsen performance. The new double-blind study tackles previous contradictory research findings related to the efficacy of ketone supplements, which have gained popularity among athletes seeking a competitive advantage; it is known that natural ketones created through diet can serve as fuel for muscles.

Some previously published studies had shown the supplements improve performance, while others have reported they had no effect or even worsened performance.

“One of the main perceived benefits is that ketones may serve as an alternative fuel source during exercise or potentially alter the utilization of other major fuel such as carbohydrates and fats, and in turn enhance endurance capacity,” explained Martin Gibala, supervising author of the study. “But our findings suggest that isn’t the case.”

The McMaster researchers recruited trained endurance athletes who cycled five or more hours per week, selecting them because their athletic performance is consistent from day to day. The experiment was conducted in a lab, but simulated race conditions and the participants prepared as they normally would for a cycling competition.

Each participant completed two trials that differed only in the drink provided before they completed a 20-minute cycling time trial that closely predicts 40-km race performance.
The drinks contained either a ketone supplement or a similar-tasting placebo.

“The main observation from this study was that the speed that the cyclists could sustain during the test was lower after drinking the ketone supplement compared to the placebo,” said lead author Devin McCarthy.

Researchers say the findings align with their previous work that found ketone supplements increased cardiorespiratory stress during exercise.

Reference:

McCarthy, et al. “Acute Ketone Monoester Supplementation Impairs 20-min Time-Trial Performance in Trained Cyclists: A Randomized, Crossover Trial. ”International Journal of Sport Nutrition and Exercise Metabolism, 2023; 33 (4): 181.

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