Exogenous Ketone Bodies and Endurance Exercise Performance: Is it Worth the Hype?

Abstract

There has been much consideration over whether exogenous ketone bodies have the capacity to enhance exercise performance through altered substrate metabolism. This systematic review aimed to determine the effects of both ketone precursors and monoesters on endurance exercise performance. A systematic search was conducted in PubMed, SPORTDiscus, and CINAHL for randomized controlled trials investigating endurance performance outcomes in response to ingestion of a ketone supplement compared to a nutritive or non-nutritive control in humans. A meta-analysis was performed to determine the standardized mean difference between interventions using a random-effects model. Hedges’ g and 95% confidence intervals (CI) were reported. The search yielded 569 articles, of which 8 were included in this review (80 participants; 77 men, 3 women). When comparing endurance performance amongst all studies, no significant differences were found between ketone and control trials (Hedges g=0.136; 95% CI, -0.195, 0.467; p=0.419). Sub-analyses based on type of endurance tests showed no significant differences in time to exhaustion (Hedges g=-0.002; 95% CI, -0.312, 0.308; p=0.989) or time trial (Hedges g=0.057; 95% CI, -0.282, 0.395; p=0.744) values. Based on these findings, exogenous ketone precursors and monoesters do not significantly improve endurance exercise performance. While all studies reported an increase in blood ketone concentrations after ingestion, ketone monoesters appear to be more effective at raising concentrations than precursors.