Gut microbiota and its relationship with Physical Activity in Spanish Adults: Findings from the MIVAS 3 Study

Background Physical inactivity affects nearly one-third of the global population and ranks as a leading risk factor for chronic diseases, while the gut microbiota has emerged as a critical modulator of metabolic health and inflammation. In this context, emerging evidence points to exercise as a key influencer of microbial diversity and function, yet large-scale studies in real-world populations remain limited. Objective The main objective is to evaluate the association between moderate to vigorous physical activity (MVPA) and gut microbiota Methods The MIVAS study was a cross-sectional analysis of 1015 Spanish adults (males and females) aged 45–74 years from primary care centers. Participants were stratified into tertiles based on weekly MVPA minute, measured using ActiGraph GT3X accelerometer (Pensacola, FL, USA). The gut microbiome composition was determined by 16S rRNA sequencing (V5-V6 region, Illumina MiSeq). Results Participants with higher levels of moderate-to-vigorous physical activity (MVPA) showed greater alpha diversity, measured by the Shannon index, with a progressive increase across tertiles. They also exhibited a distinct beta diversity profile (PERMANOVA p = 0.007). These findings remained significant after adjustment for age, sex, Mediterranean diet adherence, BMI, and other potential confounders. In the fully adjusted ANCOM-BC models, only a limited number of genera remained significantly associated with MVPA tertiles, including [Eubacterium] xylanophilum group, Butyribacter, Romboutsia, and Phascolarctobacterium. Conclusions These findings suggest regular MVPA fosters a functionally favorable microbiota shift, supporting exercise as a practical, non-pharmacological tool for cardiometabolic prevention in clinical practice. Future longitudinal studies should explore causality and metabolomics correlates.