Effect of Physical Activity on the Association Between Diet and Constipation: Evidence From the National Health and Nutrition Examination Survey 2007-2010

Background/Aims Previous studies have shown that diet and physical activity can influence constipation. However, the combined effect of diet and physical activity on constipation remains unclear. Methods Constipation was defined based on stool consistency and frequency, while overall diet quality was assessed using Healthy Eating Index (HEI)-2015 scores. Participants were categorized into low (metabolic equivalent [MET]-min/wk < 500) and high physical activity groups (MET-min/wk >= 500). The association between diet and constipation across physical activity groups was analyzed using survey logistic regression and restricted cubic splines. Results Higher HEI-2015 scores were associated with reduced constipation risk in the high physical activity group when constipation was defined by stool consistency (odds ratio [OR], 0.98; 95% confidence interval [CI], 0.97-0.99). However, in the low physical activity group, increased HEI-2015 scores did not significantly affect constipation risk (OR, 1.01; 95% CI, 0.97-1.05). Similar results were found when constipation was defined based on stool frequency. In the high physical activity group, increased HEI-2015 scores were significantly associated with a reduced constipation risk (OR, 0.96; 95% CI, 0.94-0.98). Conversely, in the low physical activity group, increased HEI-2015 scores did not affect the risk of constipation (OR, 0.96; 95% CI, 0.90-1.03). Conclusions Our findings suggest that a higher HEI-2015 score is negatively associated with constipation among individuals with high physical activity levels but not among those with low physical activity levels. This association was consistent when different definitions of constipation were used. These results highlight the importance of combining healthy diet with regular physical activity to alleviate constipation.