Effects of a 6 Week Aerobic Exercise Intervention on Gut Bacterial Metabolites in Lean and Obese Adults

Abstract

IntroductionDietary changes have been shown to significantly alter the composition and metabolic function of the gut microbiota in both mice and humans; however, study of the effects of exercise alone on the gut microbiota and microbial metabolites has been limited to mice. Short chain fatty acids (SCFAs) are bacterial metabolites with numerous downstream effects on the host, influencing satiety, inflammation, and adiposity. Here, we characterized the effects of an aerobic exercise intervention on fecal SCFA output in lean and obese humans.MethodsPreviously sedentary but otherwise healthy adults (n=11 lean; n=4 obese) underwent a six week aerobic exercise intervention. Participants performed 3 exercise sessions per week on a bike and/or treadmill, starting with 30 min at 60% HRR and building up to 60 min at 75% HRR by week 6. Fecal samples were collected before and after the intervention, preceded by a 3‐day control diet. Approximately 0.1 g of fecal samples was immediately stabilized in metaphosphoric acid until SCFA analysis by gas chromatography/mass spectrometry (GC/MS).ResultsSix weeks of exercise caused a significant increase in the fecal concentration of butyrate, acetate, and propionate (p<0.01), among lean individuals. The changes in acetate and butyrate concentrations were strongly correlated to changes in lean mass as a result of training, an effect driven by the lean individuals (r=.633 p<0.029 and r=0.854, p<0.01, respectively). However, exercise training failed to increase fecal SCFA concentration in our small sample of obese individuals (p>0.05).ConclusionA 6‐week aerobic exercise intervention is sufficient to increase fecal SCFA concentrations in lean, adult humans. This effect was not observed in obese individuals, however, and thus suggests that exercise‐induced metabolic changes within the gut may be influenced by obesity status