Association between physical activity and risk of nonalcoholic fatty liver disease: a meta-analysis

Increased physical activity (PA) is a key element in the management of patients with nonalcoholic fatty liver disease (NAFLD); however, its association with NAFLD risk has not been systematically assessed. This meta-analysis of observational studies was to quantify this association with dose-response analysis.

Electronic databases were searched to January 2017 for studies of adults reporting the risk of NAFLD in relation to PA with cohort or case-control designs. Studies that reported sex-specific data were included as separate studies. The overall risk estimates were pooled using a random-effects model, and the dose-response analysis was conducted to shape the quantitative relationship.

A total of 6 cohort studies from 5 articles with 32,657 incident NAFLD cases from 142,781 participants, and 4 case-control studies from 3 articles with 382 NAFLD cases and 302 controls were included. Compared with the lowest PA level, the highest PA level was associated with a risk reduction of NAFLD in cohort [RR (risk ratio) 0.79, 95% CI (confidence interval) 0.71-0.89] and case-control studies [OR (odds ratio) 0.43, 95% CI 0.27-0.68]. For cohort studies, both highest and moderate PA levels were superior to the light one in lowering NAFLD risk (p_{for interaction} = 0.006 and 0.02, respectively), and there was a log-linear dose-response association (p_{for nonlinearity} = 0.10) between PA and NAFLD risk [RR 0.82 (95% CI 0.73-0.91) for every 500 metabolic equivalent (MET)-minutes/week increment in PA].

Increased PA may lead to a reduced risk of NAFLD in a dose-dependent manner, and the current guideline-recommended minimum PA level that approximates to 500 MET-minutes/week is able to moderately reduce the NAFLD risk.