LAUSR

Background/objectives The purpose of this study was to examine the association between muscle weakness and non-alcoholic fatty liver disease (NAFLD), and whether the association is partly explained by insulin resistance or inflammation. Subjects/methods Subjects were 3922 adults who participated in the 2015 Korea National Health and Nutrition Examination Survey. Relative grip strength (rGS; calculated as maximal grip strength divided by BMI) was used to predict NAFLD defined by NAFLD liver fat score. Participants were classified into four groups according to the quartiles of rGS distribution (Q1–Q4). Insulin resistance was assessed by triglycerides and glucose (TyG) index. Inflammation was measured with C-reactive protein (CRP). Fibrosis was assessed by the Fibrosis-4 index (FIB-4) and the NAFLD fibrosis score. Results rGS had significant negative associations with TyG index and CRP (all p  < 0.001). rGS was a significant predictor of NAFLD (OR, 0.54–0.19 in Q2–Q4 men; OR, 0.54–0.08 in Q2–Q4 women, all p  < 0.001). Adjustment for other participant factors did not substantially affect the results. Addition of TyG index changed the estimates for NAFLD slightly and addition of CRP increased the ORs by 10–20% in Q3–Q4 women. In the subpopulation with NAFLD ( n  = 946), rGS showed strong inverse relationships with FIB-4 and NAFLD fibrosis score (all p  < 0.001). Conclusions Grip strength was inversely associated not only with the risk of NAFLD but also with its severity. Insulin resistance and inflammation explained only a small portion of the association between grip strength and NAFLD risk.