Exercise improves gut microbial metabolites in an intensity-dependent manner: a pooled analysis of randomized controlled trials.
Level 2 - randomized trial
Pooled individual participant analysis of three randomized controlled trials
PubMed 41320950 · doi:10.1080/19490976.2025.2579354
What was done
A pooled analysis of data from three randomized controlled trials evaluated 113 patients with obesity and metabolic syndrome (MetS). Participants were allocated to 12 weeks of low-volume high-intensity interval training combined with single-set resistance training (HIGH-EX), moderate-intensity interval training combined with resistance training (MOD-EX), or a non-exercising control group (CON). Investigators measured fecal short-chain fatty acid (SCFA) concentrations, cardiorespiratory fitness (VO2max), muscle strength, high-sensitivity C-reactive protein (hsCRP), MetS severity z-score, and blood lactate during interval sessions.
What was found
Both HIGH-EX and MOD-EX improved VO2max (+4.2 and +2.7 mL/kg/min), muscle strength (+19% to +29%), hsCRP (-2.2 and -1.3 mg/L), and MetS z-score (-1.1 and -0.5 units). However, only HIGH-EX significantly increased total fecal SCFAs (+30%), acetate (+27%), propionate (+28%), and butyrate (+43%). Mean exercise blood lactate concentrations correlated with SCFA increases (r = 0.68, p < 0.001). The control group showed no changes.
Why it matters
While both moderate and high-intensity training confer cardiometabolic and fitness benefits, microbial metabolite enhancement appears intensity-dependent, potentially mediated by training-induced lactate production.
Limits
The total sample size is modest (113 participants across three trials), and sample sizes per individual arm are not reported in the abstract. Dietary intake control, detailed microbiome taxonomic shifts, and long-term durability of the metabolite changes beyond 12 weeks were not reported.
Cited by
- supports Exercise has been shown to increase butyrate-producing bacteria in the gut microbiome.