Relative Fat Mass and Constipation in U.S. Adults: A Cross-Sectional Study of 11,380 Participants From NHANES 2005-2010.

Abstract

Background Constipation is a common gastrointestinal disorder closely associated with obesity. Relative Fat Mass(RFM) is a newer anthropometric index that offers a more precise reflection of body fat distribution than traditional methods. Despite its advantages, the potential link between RFM and the likelihood of experiencing constipation has not been thoroughly examined. This study was therefore designed to explore the association between RFM and constipation Methods Data were obtained from the 2005-2010 cycles of the National Health and Nutrition Examination Survey (NHANES). Constipation was defined using the Bristol Stool Form Scale and questionnaire responses. Weighted multivariable logistic regression models were employed to evaluate the association between RFM and constipation. Propensity score matching (PSM) was used to balance baseline covariates between groups. Analyses were conducted both before and after PSM to test the robustness of the findings. Smooth curve fitting and threshold effect analyses were conducted to explore potential nonlinear relationships. Subgroup analyses and interaction tests were used to assess possible heterogeneity across different population strata. Results A total of 11,380 participants were included in the final analysis, among whom 1,206 were classified as having constipation. Logistic regression revealed that in the fully adjusted model, each one-unit increase in RFM was associated with a 2.9% reduction in the odds of constipation (OR = 0.971, 95%CI: 0.956-0.986, p = 0.0011). Furthermore, PSM analyses confirmed the robustness of the results. The inverse association between RFM and constipation was more pronounced among individuals aged > 45 years, those with hypertension, and those who did not consume alcohol (all p for interaction < 0.05). Smooth curve fitting and threshold effect analysis indicated a nonlinear relationship, with an inflection point at an RFM of 36.06. Conclusion Our study suggests a significant inverse association between RFM and constipation. Further prospective studies are warranted to validate this relationship.