Ketone monoester reduces blood glucose, exogenous CHO oxidation, and oxidation efficiency in trained male cyclists when fed 120 g/h of CHO during exercise

Martyn, HJ, Cameron, NE, Edmondson, JA, Phelan, MM, Gonzalez, JT, Shepherd, SO, Pugh, JN ORCID: 0000-0002-5930-4709, Owens, DJ ORCID: 0000-0002-1908-8677 and Morton, JP ORCID: 0000-0003-2776-2542 (2026) Ketone monoester reduces blood glucose, exogenous CHO oxidation, and oxidation efficiency in trained male cyclists when fed 120 g/h of CHO during exercise. Journal of Applied Physiology (1985), 140 (5). pp. 1373-1388. ISSN 8750-7587

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Abstract

We examined the effects of ketone monoester (KME) and carbohydrate (CHO) coingestion on exogenous CHO oxidation (via U-13C-enriched glucose-fructose drinks), metabolomic responses, and exercise capacity. In a randomized crossover design (after 36 h of CHO loading and pre-exercise meal of 12 and 2 g·kg−1, respectively), eight trained male cyclists (V̇o2max; 66 ± 7 mL·kg−1·min−1) ingested 0 g·h−1 (PLA), 120 g·h−1 CHO (CHO), or 120 g·h−1 CHO + 75-g ketone monoester (CHO + KME) during 3 h of cycling at power outputs corresponding to 95% of lactate threshold (LT) followed by exercise to exhaustion at 150% LT. Mean blood glucose concentrations during exercise were different between all pairwise comparisons (P < 0.05) such that CHO > CHO + KME > PLA (4.9 ± 0.3, 4.4 ± 0.2, 3.7 ± 0.4 mmol·L−1, respectively). Mean exogenous CHO oxidation (1.35 ± 0.15 vs. 1.50 ± 0.16 g·min−1, P < 0.01) and oxidation efficiency was lower in CHO + KME (67 ± 7%) compared with CHO (75 ± 6%, P < 0.01). Exercise capacity was greater (P < 0.05) in CHO (349 ± 189 s) and CHO + KME (319 ± 225 s) compared with PLA (75 ± 105 s), though no differences were evident between CHO and CHO + KME (P > 0.05). Ketone monoester ingestion increased abundance of metabolites associated with carbohydrate metabolism (glucaric acid) and protein turnover (3-methylhistidine). We conclude that ketone monoester ingestion does not enhance exercise capacity and reduces blood glucose concentrations, exogenous CHO oxidation, and oxidation efficiency when compared with CHO alone.

NEW & NOTEWORTHY To promote exercise performance, endurance athletes frequently consume CHO during exercise at ingestion rates of 90–120 g·h−1. Here, we report for the first time that coingestion of a ketone monoester before and during prolonged cycling reduces blood glucose concentrations, exogenous CHO oxidation, and oxidation efficiency compared with CHO alone (120 g·h−1; 1:0.8 ratio of maltodextrin and fructose). Ketone monoester ingestion also increased plasma abundance of metabolites associated with carbohydrate metabolism (glucaric acid) and protein turnover (3-methylhistidine).

Item Type:	Article
Uncontrolled Keywords:	fructose; ketones; maltodextrin; metabolomics; stable isotopes; Humans; Esters; Lactic Acid; Ketones; Dietary Carbohydrates; Glucose; Blood Glucose; Exercise; Cross-Over Studies; Oxidation-Reduction; Oxygen Consumption; Bicycling; Adult; Male; fructose; ketones; maltodextrin; metabolomics; stable isotopes; Humans; Male; Oxidation-Reduction; Blood Glucose; Ketones; Dietary Carbohydrates; Adult; Bicycling; Exercise; Cross-Over Studies; Lactic Acid; Glucose; Oxygen Consumption; Esters; 42 Health Sciences; 4207 Sports Science and Exercise; Physical Activity; Nutrition; 7 Affordable and Clean Energy; Humans; Male; Oxidation-Reduction; Blood Glucose; Ketones; Dietary Carbohydrates; Adult; Bicycling; Exercise; Cross-Over Studies; Lactic Acid; Glucose; Oxygen Consumption; Esters; 06 Biological Sciences; 11 Medical and Health Sciences; Physiology; 31 Biological sciences; 32 Biomedical and clinical sciences; 42 Health sciences
Subjects:	R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions:	Sport and Exercise Sciences
Publisher:	Amercian Physiological Society
Date of acceptance:	1 April 2026
Date of first compliant Open Access:	19 August 2026
Date Deposited:	19 Aug 2026 13:23
Last Modified:	19 Aug 2026 13:23
DOI or ID number:	10.1152/japplphysiol.01072.2025
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29160

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