Muscle fat content is strongly associated with NASH: a longitudinal study in patients with morbid obesity.

Abstract Background and aims To evaluate the association between muscle mass and fatty infiltration and biopsy-assessed NAFLD in patients with obesity. Materials and Methods At inclusion (n=184) and 12 months after a dietary intervention (n=15) or a bariatric surgery (n=24), we evaluated NAFLD with liver biopsy, skeletal muscle mass index with computed tomography (CT-SMI) and bioelectrical impedance analysis (BIA-SMI). We developed an index to evaluate absolute fat content in muscle (skeletal muscle fat index; SMFI) from CT-based psoas muscle density (SMFIPsoas). Results Muscle mass was higher in patients with NAFLD than in those without (CT-SMI 56.8±9.9 vs 47.4±6.5 cm2/m, 2 p Conclusions Muscle fat content, but not muscle mass, is strongly and independently associated with NASH. All individuals who achieved a ≥11% decrease in SMFIPsoas after intervention improved their NASH. These data call to explore muscle fatty infiltration as a potential marker for (and perhaps a pathophysiological contributor to) NASH. Lay Summary The fat content in skeletal muscles is highly reflective of the severity of non-alcoholic fatty liver disease (NAFLD) in patients with morbid obesity. In particular, muscle fat content is strongly associated with non-alcoholic steatohepatitis (NASH) and decreases upon NASH improvement. These data call to explore muscle fatty infiltration as a potential marker and perhaps a pathophysiological contributor to NASH.