Physical Activity and Irritable Bowel Syndrome: The Role of Evolutionary Mismatch in Chronic Disease Risk

Rising rates of noncommunicable diseases have been attributed to evolutionary mismatch between past physical activity and sedentary, post-industrial behavior. Epidemiologic research suggests that sedentism increases irritable bowel syndrome (IBS) risk. We test this association with a population sample to assess whether physical activity mismatch is associated with IBS.

This study recruited Pennsylvanians (age- and sex- matched to state population) to complete an online survey documenting digestion, demographics, and physical activity. IBS was diagnosed using Rome IV criteria, and data were analyzed using binary logistic regression.

The sample included 921 individuals (55.3% F; mean age = 38.78) with an IBS prevalence of 28.8%. Exercise vigor (none/low) was significantly associated with increased IBS risk [OR 1.469, 95% CI: 1.168-2.126, p = 0.0154], though other measures of exercise were not. BMI was a strong predictor of IBS continuously (sample mean BMI = 28.61) [OR 1.029, 95% CI: 1.011-1.048, p = 0.002], with higher BMI increasing IBS risk, especially for those overweight (25 < BMI < 30) [OR 1.734, 95% CI: 1.129-2.664, p = 0.012] or obese (BMI > 30) [OR 2.062, 95% CI: 1.361-3.125, p = 0.001]. BMI significantly mediated the relationship between exercise vigor and IBS.

Most research finds IBS is an illness driven by the environment, with exercise playing a protective role in disease risk. Our findings suggest that mismatch due to exercise levels alone is likely not a major driver of disease; instead, IBS may be driven by longitudinal effects of exercise (proxied here by BMI) alongside other environmental and behavioral factors contributing to energetic balance, such as diet and stress.