Sex-specific marathon-induced metabolome changes

Abstract Background: Marathon running imposes substantial metabolic stress, with sex-specific responses driven by differences in substrate utilisation, hormonal regulation, and muscle phenotype. Despite this, sex-specific metabolomic data remain limited, due to historical underrepresentation of female athletes. The aim of the study was to better understand how marathon running affects metabolism in male and female endurance athletes. Methods: Serum samples from male (n = 19) and female (n = 12) endurance athletes were analysed pre- and post-marathon using a multi-platform untargeted metabolomics approach, combining nuclear magnetic resonance spectroscopy and two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. Two-way ANOVA identified 21 metabolites that differed significantly ( p < 0.05) across timepoints and sex. Results: Post-marathon, males exhibited higher concentrations of ketone bodies, tricarboxylic acid cycle intermediates, branched-chain amino acids, and α-keto acids, consistent with greater reliance on lipid and amino acid catabolism for energy production. Elevated creatinine further reflected increased muscle stress and damage. Females however, showed higher creatine concentrations than males at both pre- and post-marathon timepoints, suggesting sex differences in creatine synthesis and breakdown. Gut microbiome-associated metabolites, including arabitol, methanol, and 3-phenylpropionic acid, also differed between sexes across timepoints, highlighting interactions between the gut microbiome, exercise, and metabolism. These largely sex-specific metabolic responses are driven by differences in hormonal regulation, substrate utilisation, and skeletal muscle phenotype, which together influence the balance between lipid, carbohydrate and amino acid use during prolonged endurance exercise. Conclusions: Collectively, these findings indicate that males rely more heavily on circulating fatty- and amino acids during endurance exercise, whereas females demonstrate more efficient lipid utilisation with reduced dependence on amino acid catabolism. This study provides novel insights into sex-specific metabolic changes associated with marathon running and advances our understanding of male and female metabolite responses following a marathon. These findings support the need for sex-specific strategies for optimising performance, recovery and long-term health in both male and female athletes.