Too much intense exercise can mess up the good bacteria in your gut and make your gut 'leaky,' letting harmful stuff into your body and causing stomach problems and body-wide inflammation.
Evidence from Studies
No evidence studies found yet.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Provide pooled estimates of microbiome changes and gut permeability in overtrained vs. healthy athletes.
A systematic review and meta-analysis of 10+ longitudinal studies with fecal microbiota sequencing and lactulose/mannitol urinary excretion testing in elite endurance athletes undergoing periodized training, comparing those who develop OTS versus controls, with at least 500 participants total.
Establish temporal sequence between training load, microbiome changes, gut permeability, and OTS onset.
A 6-month prospective cohort study of 150 professional cyclists, collecting monthly stool samples for microbiome analysis, intestinal permeability tests, training logs, and OTS screening (POMS, performance), to model the progression from normal training to OTS.
Compare gut microbiome composition and permeability markers between athletes with and without OTS at a single time point.
A cross-sectional study of 80 elite runners (40 with OTS, 40 matched controls), analyzing fecal microbiota (16S rRNA), serum zonulin, and urinary lactulose/mannitol ratio, along with dietary intake and training history.
Synthesize current understanding and propose mechanistic models of exercise-induced gut dysfunction.
A narrative review by gastroenterology and sports science experts summarizing evidence on exercise, microbiome, and intestinal barrier function, discussing implications for athlete health and performance.