Exercise, specifically regular aerobic exercise, significantly lowers intrahepatic lipid (IHL) and serum alanine aminotransferase (ALT) levels in patients with nonalcoholic fatty liver disease (NAFLD), according to study findings published in Digestive and Liver Disease.
Researchers conducted a systematic review and meta-analysis of the literature covering MEDLINE, Cochrane CENTRAL, Embase, KMbase, and the Korean Studies Information Service System databases from inception until April 2022. They identified a total of 1708 studies that assessed the effects of exercise on patients with NAFLD. They selected 11 relevant randomized controlled trials that comprised 577 participants for the final analysis.
The researchers analyzed the effect of various types of exercise on IHL levels (11 studies), ALT levels (9 studies), serum aspartate aminotransferase (AST) levels (6 studies), gamma-glutamyl transferase (GGT) levels (6 studies), body mass index (BMI; 8 studies), and insulin resistance (5 studies).
Exercise correlated with significantly reduced IHL levels (mean difference from baseline, -2.03; 95% CI, -3.26 to -0.79; P =.001) and ALT levels (mean difference from baseline: -4.17; 95% CI, -6.60 to -1.73; P =.0008). No significant changes in AST levels (P =.28), GGT levels (P =.16), BMI (P =.35), or insulin resistance (P =.77) due to exercise were observed.
The researchers also assessed the effects of exercise duration and type of exercise on liver disease biomarkers. Participants with NAFLD who continued to exercise for more than 3 consecutive months demonstrated significant improvements in IHL levels compared with those who exercised for less than 3 months (mean difference between groups, -3.62; 95% CI, -5.76 to -1.48; P =.0009).
Aerobic exercise (mean difference, -2.37; 95% CI, -3.93 to -0.81; P =.003) resulted in significant changes to IHL levels in contrast with resistance exercise, which insignificantly lowered IHL levels (mean difference, -1.88; 95% CI, -4.08 to 0.33; P =.09).
Study limitations include the lack of information regarding histological improvement of NAFLD, an insufficient number of included studies on relevant subgroups rendering meta-analysis of these subgroups impossible, and the lack of data on other measurements including AST and GGT levels, insulin resistance, and BMI.
“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,” the researchers conclude.
Nam H, Yoo JJ, Cho Y, et al. Effect of exercise-based interventions in nonalcoholic fatty liver disease: A systematic review with meta-analysis. Dig Liver Dis. Published online January 16, 2023. doi:10.1016/j.dld.2022.12.013