Ketone Supplementation in Trained and Physically Active Individuals: Effects on Athletic Performance and Metabolic Variables—A Systematic Review

Exogenous ketone supplementation has emerged as a potential ergogenic strategy for trained and physically active individuals, prompting increasing research into its effects on exercise performance and metabolism. This systematic review evaluated the effects of ketone supplementation on athletic performance, metabolic variables, and physiological responses in trained and physically active populations. Searches were conducted in EBSCOhost, PubMed, and Web of Science following PRISMA 2020 guidelines. Peer-reviewed controlled studies published between 2018 and December 2025 were included. Twenty-six studies met the eligibility criteria. Ketone supplementation consistently increased circulating β-hydroxybutyrate concentrations and modified glucose, lactate, and acid–base balance. Effects on exercise performance were heterogeneous, with some studies reporting improvements in time-trial performance and cognitive function, whereas others found no benefit or even impaired performance. Co-ingestion with sodium bicarbonate attenuated metabolic acidosis and occasionally enhanced performance outcomes. Ketone supplementation also influenced cardiorespiratory responses and fluid regulation, and may promote muscular angiogenesis during periods of training overload. Overall, current evidence remains heterogeneous and does not support definitive conclusions regarding ergogenic efficacy, which appears to depend on exercise intensity, participant characteristics, supplementation protocols, and co-ingestion strategies.