Resistance Training Reshapes Gut Microbiome in Sedentary Adults Original paper

What was studied?

This longitudinal intervention study investigated whether structured resistance training induces significant changes in the gut microbiome composition and diversity of sedentary, healthy adults. Over 150 participants completed an 8‑week supervised resistance training program (2–3 sessions per week) using digitally controlled EGYM Smart Strength machines. The researchers collected faecal samples at baseline (week 0), mid‑intervention (week 4), and post‑intervention (week 8) for 16S rRNA gene amplicon sequencing, along with targeted metabolomics at weeks 0 and 8. They also recorded detailed session‑level training data (weights, repetitions, load metrics) and assessed fitness parameters (strength gains, BioAge Strength, activity points). The study uniquely linked individual strength trajectories to microbial dynamics, testing whether resistance training reshapes gut microbiome composition in a dose‑dependent manner.

Who was studied?

A total of 205 sedentary individuals were initially enrolled; 150 completed the full protocol and were included in the final analysis (85 female, 63 male, age range 24–61 years, mean 42 years). Participants were recruited from the University of Tübingen and surrounding areas in Germany. All were sedentary (<1 hour of regular physical activity per week for the past 6 months), healthy, and normal to slightly overweight bmi (mean 24.5 kg m²). exclusion criteria included antibiotic use or improper stool storage. participants were randomly assigned either a resistance training (higher repetitions, lower weight) muscle‑building (lower higher regimen. both groups similar in total load, points, dietary patterns, allowing pooling most analyses. maintained stable diet throughout study. this large, well‑characterised cohort allowed authors robustly test whether resistance reshapes gut microbiome independently changes.< p>

Most important findings

The study found that resistance training did not significantly alter alpha diversity (Shannon index, p>0.5) or overall beta diversity across all participants. However, within‑individual microbial community shifts (Bray‑Curtis distances) were significantly correlated with strength improvement (Pearson r = 0.167, p = 0.0004). When participants were stratified by average strength gain into high‑responders (≥33% gain, top 20%) and low‑responders (≤12.2% gain, bottom 20%), high‑responders showed significantly larger within‑subject beta diversity shifts (p = 0.08). Differential abundance analysis in high‑responders revealed time‑dependent microbial changes: at week 4, 9 Amplicon Sequence Variants (ASVs) were enriched and 4 depleted; by week 8, 16 ASVs were enriched and 11 depleted (ANCOM‑BC2, ≥2‑fold change, p≤0.05). Key enriched taxa included:

Notably, these shifts occurred in the absence of dietary changes (self‑reported diet remained stable), indicating that resistance training reshapes gut microbiome independently of diet. Despite these taxonomic changes, faecal metabolomics (including SCFAs, amino acids, bile acids) showed no significant alterations. The authors hypothesise that functional changes may be subtle, localised to the mucosal interface, or require longer adaptation.

Key implications

For clinicians, this study provides high‑quality evidence that structured resistance training can beneficially modulate the gut microbiome, particularly in individuals who achieve substantial strength gains (≥33% improvement over 8 weeks). The enrichment of Faecalibacterium and Roseburia hominis – both strongly associated with anti‑inflammatory, SCFA‑producing, and gut‑barrier‑enhancing properties – suggests that resistance training may confer gut health benefits similar to those seen with endurance exercise. This is clinically relevant for sedentary patients, those with low‑grade inflammation, metabolic syndrome, or age‑related gut dysfunction. Unlike endurance training, resistance training does not require prolonged time commitment or high cardiovascular fitness, making it accessible to a broader range of patients. Importantly, the absence of dietary changes in the study implies that the observed microbial shifts are directly attributable to the exercise stimulus itself. However, the lack of a non‑exercising control group limits causal inference (the study used within‑subject baseline controls). The finding that stool metabolomics did not change suggests that functional benefits may not be captured by faecal SCFA levels alone; future studies should measure circulating metabolites or mucosal markers. Clinicians can confidently recommend resistance training for overall health, with the added potential benefit of promoting a healthier gut microbiome, especially when patients achieve meaningful strength improvements. The study also highlights the importance of monitoring individual response, as only high‑responders showed clear microbial changes.