Association between predicted body composition and metabolic-associated fatty liver disease: a case-control study in a Chinese population

Objective Metabolic-associated fatty liver disease (MASLD) is a growing global health concern. Few studies have examined the independent associations of fat mass (FM) and lean body mass (LBM) with MASLD. This study investigated the associations of predicted FM, body fat percentage (BF%), LBM, and the FM-to-LBM ratio with MASLD risk in a physical examination population from China. Methods This 1:1 age- and sex-matched case-control study included 1,683 MASLD patients and 1,683 controls. Predicted FM, BF%, LBM, and FM/LBM were calculated using equations derived from the National Health and Nutrition Examination Survey (NHANES). Conditional logistic regression was used to analyze associations between body composition indices and MASLD risk after adjusting for confounders. Results Levels of BMI, blood pressure, blood lipids, fasting glucose, liver enzymes, and uric acid were significantly higher in the MASLD group (all P < 0.001). The MASLD group also had significantly higher levels of FM, BF%, LBM, and FM/LBM ( P < 0.001). After multivariable adjustment, the highest quartiles (Q4) of FM (OR = 2.77, 95% CI: 2.26–3.40), BF% (OR = 2.16, 95% CI: 1.78–2.62), LBM (OR = 1.62, 95% CI: 1.27–2.04), and FM/LBM (OR = 2.37, 95% CI: 1.99–2.83) were significantly associated with increased MASLD risk compared to the lowest quartiles (Q1) (all P < 0.001), with significant linear trends ( P for trend < 0.001). Non-linear dose-response relationships were observed ( P < 0.001). Subgroup analyses revealed stronger associations in individuals aged < 60 years, non-obese (BMI < 28 kg/m 2 ), and non-hypertensive populations. Conclusion Elevated levels of predicted FM, BF%, and FM/LBM were independently associated with increased MASLD risk, showing non-linear dose-response relationships. Higher predicted LBM was also associated with increased MASLD risk; however, this finding should be interpreted with caution. These associations were more pronounced in younger, non-obese, and normotensive individuals.