Association of Domain-Specific Physical Activities with Non-Alcoholic Fatty Liver Disease in Workers: A Focus on Gender Differences

Objectives: Occupational physical activity (OPA) and leisure-time physical activity (LTPA) have contrasting health effects, a phenomenon known as the “physical activity paradox.” We explored the domain-specific associations between physical activity and non-alcoholic fatty liver disease (NAFLD). Methods: This cross-sectional study included 20,584 Korean workers (10,846 women). Physical activity was assessed using the Global Physical Activity Questionnaire, and NAFLD was assessed using the hepatic steatosis index and the presence of metabolic dysfunction. Logistic regression models were employed to explore the association between each domain of physical activity and NAFLD. The associations are presented as odds ratios (ORs) and 95% confidence intervals (CIs). Results: The prevalence of NAFLD was 30.6% in men and 18.1% in women. For male workers, ≥300 min/week of OPA was positively associated with NAFLD (OR: 1.41; 95% CI: 1.15–1.72), while ≥300 min/week of LTPA was negatively associated with NAFLD (OR: 0.79; 95% CI: 0.67–0.93). In female workers, LTPA was negatively associated with NAFLD from a lower level (OR: 0.63; 95% CI: 0.52–0.78 for 1–149 min/week; OR: 0.71; 95% CI: 0.56–0.89 for 150–299 min/week; OR: 0.58; 95% CI: 0.43–0.78 for ≥300 min/week of LTPA), while OPA had no clear association with NAFLD. Conclusions: OPA and LTPA were differentially associated with NAFLD in workers. Domain- and sex-specific effects of physical activity should be considered for the prevention and management of NAFLD.