High-protein intake shapes physiological adaptation and gut microbiota in response to resistance training.

AIMS: High-protein diets stimulate muscle anabolism and influence gut microbiota composition, while resistance training improves neuromuscular function and metabolic health. We investigated whether dietary protein acts as the primary driver of physiological and microbial adaptations, and whether resistance training provides additional benefits. MATERIALS AND METHODS: Twenty-four male C57BL/6 mice were randomly assigned to four groups (n = 6 per group): normal control (NC), high-protein diet (HPD), normal diet with exercise (NC + EX), and high-protein diet with exercise (HPD + EX). The HPD provided 60% of total energy from protein. Resistance training consisted of progressive ladder-climbing performed three times per week for eight weeks. Physical performance was evaluated by grip strength, weight-holding capacity, rotarod performance, and functional strength performance. Gut microbiota was analyzed using 16S rRNA sequencing, and blood and tissue samples were collected for biochemical and histological analyses. KEY FINDINGS: Compared with NC, the HPD + EX group exhibited significantly enhanced physical performance, and reduced mesenteric fat mass and adipocyte size (p < 0.05). HPD alone decreased gut microbial richness, whereas the HPD + EX group did not differ significantly from the HPD group in microbial richness or overall microbiota composition. LEfSe analysis identified higher relative abundances of selected genera, including Lactobacillus and Faecalibaculum, in the HPD + EX group than in the HPD group. SIGNIFICANCE: These findings identify dietary protein as a key determinant of physiological and gut microbial adaptations, while resistance training primarily improves physical performance and may influence selected microbial taxa without restoring or stabilizing the overall microbial community. Together, these findings suggest that dietary protein and resistance training may play distinct and complementary roles in host metabolic regulation and physical function.