Association between body composition and metabolic dysfunction-associated steatotic liver disease in Chinese general population: a cross-sectional study stratified by sex and obesity status

Abstract

Background Metabolic dysfunction-associated steatotic liver disease (MASLD) is a global health challenge with rising prevalence, yet the sex- and obesity-specific associations of body composition indices—particularly the fat-free mass to fat mass (FFM/FM) ratio—with MASLD remain incompletely characterized. This study aimed to investigate sex- and obesity-related differences in body composition associations with MASLD in a Chinese general population. Methods This retrospective cross-sectional study enrolled 1,209 participants (562 males, 647 females) who underwent health check-ups at Guilin People’s Hospital between 2020 and 2022. Body composition was measured by bioelectrical impedance analysis (BIA), and MASLD was diagnosed by abdominal ultrasound using the 2023 consensus criteria. Logistic regression models assessed associations between body composition indices and MASLD, stratified by sex and obesity status. Interaction tests, restricted cubic splines (RCS), E-value calculations, and receiver operating characteristic (ROC) analyses were performed. Results Overall MASLD prevalence was 28.3%, significantly higher in males (39.9%) than in females (18.2%), particularly among the obese group (57.4% vs. 41.2%) and non-obese group (16.9% vs. 7.7%). After adjusting for confounders, a lower FFM/FM ratio was significantly associated with higher MASLD prevalence in all subgroups except the non-obese stratum, in which the association was of similar magnitude but borderline non-significant. (males: OR = 0.47, 95% CI 0.26–0.83, p = 0.009; females: OR = 0.35, 95% CI 0.13–0.95, p = 0.039; obese: OR = 0.49, 95% CI 0.26–0.92, p = 0.028; non-obese: OR = 0.46, 95% CI 0.21–1.01, p = 0.051). Interaction tests were not significant (sex: p = 0.554; obesity: p = 0.917). RCS revealed a linear dose–response relationship (overall p = 0.021; nonlinear p = 0.289). E-values ranged from 2.21 to 2.77, indicating robustness to unmeasured confounding. Waist-to-hip ratio (WHR) was independently associated with MASLD only in females (OR = 1.13, 95% CI 1.04–1.22, p = 0.003), and the combined FFM/FM + WHR model achieved the highest AUC in females (0.822). Conclusion FFM/FM ratio shows a universal protective effect against MASLD across sex and obesity strata, while WHR has sex-specific predictive value only in women. The linear dose–response relationship supports continuous monitoring of muscle-fat balance, even in normal-weight individuals. BIA-derived body composition analysis may assist in identifying high-risk individuals for MASLD in large-scale health check-ups.