Effect of exercise-based interventions in nonalcoholic fatty liver disease: A systematic review with meta-analysis

Background: The global burden of nonalcoholic fatty liver disease (NAFLD) is rapidly increasing. Aims: This study aimed to evaluate the effect of exercise on intrahepatic lipid (IHL), serum alanine aminotransferase (ALT), body mass index (BMI), and insulin resistance in NAFLD patients. Methods: We searched MEDLINE, Embase, Cochrane CENTRAL, KMbase, and the Korean Studies Information Service System through April 2022. The included studies were randomised control trials (RCTs) of exercise, in which IHL was measured using magnetic resonance imaging in adult NAFLD patients. Results: Eleven RCTs with 577 participants were included in this meta-analysis. Exercise was significantly associated with a reduction in IHL (mean difference (MD), -2.03; 95% CI, -3.26 to -0.79; P = 0.001) and a decrease in ALT (MD, -4.17; 95% CI, -6.60 to -1.73; P = 0.0008). Regarding the duration of exercise, maintaining exercise for more than 3 months significantly improved IHL (MD, -3.62; 95% CI, -5.76 to -1.48; P = 0.0009), while exercise for less than 3 months did not (MD, -1.23; 95% CI, -2.74 to 0.29; P = 0.11). BMI and insulin resistance did not improve significantly with exercise. Conclusions: We found that exercise improved IHL and ALT levels in NAFLD patients. The effect of exercise is particularly increased when one engages in exercises that last longer than 3 months.