Association between the skeletal muscle-to-visceral fat area ratio and liver fibrosis risk in patients with non-alcoholic fatty liver disease: a cross-sectional study.

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is highly prevalent and closely linked to metabolic dysfunction, with progressive liver fibrosis driving adverse outcomes. Conventional obesity metrics such as body mass index (BMI) and waist circumference inadequately capture body-composition imbalance. The skeletal muscle-to-visceral fat area ratio (SVR) integrates muscle reserve and visceral adiposity and may better reflect metabolic risk. However, large-scale evidence on SVR and fibrosis risk in Chinese patients with NAFLD is limited. This study investigated the association between the SVR and liver fibrosis risk in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

A cross-sectional study was conducted involving 661 patients with fatty liver from the Health Management Center of Peking Union Medical College Hospital (Xidan Branch) between January 2021 and November 2024. SVR was measured using a body composition analyzer, and the fibrosis-4 index (FIB-4) was calculated. Because the raw FIB-4 score was right-skewed and the residuals from the raw FIB-4 linear model were not normally distributed, log(FIB-4) was used as the continuous outcome. Hierarchical multivariable linear regression was used to analyze the association between SVR and log(FIB-4), and the mediating role of BMI was tested using the bootstrap method.

RESULTS

The raw FIB-4 score was markedly right-skewed (skewness = 1.440, Shapiro-Wilk p < 0.001), whereas the distribution of log(FIB-4) was substantially improved after natural logarithmic transformation (skewness = -0.123, Shapiro-Wilk p = 0.444). In the unadjusted model, SVR was inversely associated with log(FIB-4) (B = -0.067, 95% CI -0.109 to -0.025, p = 0.002). In the fully adjusted model including BMI, the inverse association between SVR and log(FIB-4) became stronger. Mediation analysis revealed a significant suppression effect of BMI, with a positive indirect effect and a negative direct effect (indirect effect = 0.041, direct effect = -0.108). Subgroup analysis showed that the suppression effect was observed in the higher-BMI subgroup and in both men and women, but not in the lower-BMI subgroup.

CONCLUSION

Higher SVR was associated with lower log(FIB-4) among patients with NAFLD, and BMI appeared to suppress part of this association. These findings suggest that SVR may provide body-composition information beyond BMI in FIB-4-based risk assessment, but longitudinal studies with more precise fibrosis assessment are needed for validation.