Exercise & Sports Performance

The Effects of 31-Day Exogenous Ketone Consumption on Running Performance, Cognitive Function, Metabolism, Body Composition, Hemodynamics, and Mood in Recreational Runners: A Randomized-Control Trial

Exogenous ketone supplements can rapidly raise circulating beta-hydroxybutyrate (BHB), but their longer-term effects on exercise performance, cognition, and metabolic health remain unclear. This randomized controlled trial evaluated the effects of 31 days of ketone monoester (KME) supplementation on running performance, metabolism, cognition, mood, and body composition in recreational runners.

Eighteen recreational runners (9 men, 9 women) were randomized in a single-blind parallel design to consume either a ketone monoester supplement or an isocaloric placebo three times daily for 31 days. Each dose provided 30 grams of ketone monoester (90 grams per day in total), and participants maintained their usual diet and training routines.

Primary outcomes included 5-km running performance, graded exercise testing, cognitive function (Stroop and task-switching tests), mood and quality-of-life measures, metabolic biomarkers, and body composition. Blood glucose and ketone levels were measured repeatedly throughout the study.

Key Findings:

Running Performance

• 31 days of ketone supplementation did not improve 5-km running time compared with placebo.
• During graded exercise testing, absolute VO₂ was preserved in the ketone group, while it declined in the placebo group.

Cognitive Function

• Reaction times improved in several executive function tests.
• Stroop incongruent reaction times remained stable with ketones but worsened with placebo.
• Correct response times in a task-switching test improved by ~182 ms in the ketone group, indicating faster cognitive processing.

Metabolic Effects

• Ketone supplementation reliably elevated circulating β-hydroxybutyrate to ~3.0 mmol/L after ingestion.
• Post-meal blood glucose was ~15% lower with ketone supplementation compared with placebo.
• Fasting glucose levels were also modestly lower by week four in the ketone group.

Mood and Quality of Life

• No significant differences were observed in depression, stress, quality of life, or most mood measures.

Body Composition and Cardiovascular Measures

• Body weight, body composition, and blood pressure did not significantly change between groups.

Adverse Effects

• Some participants experienced increased lower gastrointestinal symptoms during week three of supplementation.

Conclusion

Thirty-one days of ketone monoester supplementation did not improve running performance but produced measurable metabolic and cognitive effects. Blood ketones increased, post-prandial glucose decreased, executive function improved in some tests, and oxygen uptake during graded exercise was preserved. These findings suggest potential metabolic and neurological effects that warrant further investigation.