Abstract

Objective: To investigate the relationship between longitudinal changes in body composition and liver disease severity in children with metabolic dysfunction-associated steatotic liver disease (MASLD).

Study design: This longitudinal, single-center, retrospective analysis included patients aged <20 years followed for MASLD who had had ≥2 bioelectrical impedance analyses (BIA) performed. MASLD regression was defined as alanine aminotransferase (ALT) normalization or reduction >50% from baseline. Fat and skeletal muscle mass were adjusted for size by calculating respective indices (dividing by height²). Logistic and linear regressions were used to determine the independent relationship between changes in body composition over time and serologic markers of liver disease severity.

Results: 258 patients (75% male, 50% Hispanic) were included with median age of 14 years (IQR: 11, 16) at the time of first BIA. Median body mass index (BMI) z-score at baseline was 2.33 (IQR: 2.04, 2.62). Median time from first to last BIA was 12 months (IQR: 6, 24). A decrease in fat mass index was independently associated with reductions in ALT and gamma glutamyl transferase (GGT) and increased odds of MASLD-regression (OR: 0.55, p<0.001). Fat mass index reduction was superior to BMI z-score in predicting MASLD-regression. Change in skeletal muscle mass index was not associated with change in ALT or GGT.

Conclusions: Changes in fat mass, not skeletal muscle mass, are associated with serologic markers of liver injury in youth with MASLD. Fat mass changes outperform BMI z-score changes in predicting MASLD regression. BIA can serve as an adjunct biomarker of liver disease progression.