Higher intensity exercise associated with greater decrease in nonalcoholic fatty liver disease risk

1. This analysis of a population-based cohort found that those who engaged in high and moderate decreasing amounts of vigorous physical activity (VPA) over twenty-five years decreased their relative risk of developing nonalcoholic fatty liver disease (NAFLD) by 41%, emphasizing that vigorous (as opposed to moderate) physical activity in early adulthood provided the most benefit. 

Evidence Rating Level: 2 (Good)

Chronic liver disease is most commonly attributed to non-alcoholic fatty liver disease (NAFLD) and the current primary therapeutic and preventative recommendations for this condition include lifestyle modification. While physical activity is itself beneficial for NAFLD, this study is one of the first to analyze how different long-term patterns in exercise (i.e., vigorous- versus moderate-intensity) impact NAFLD trajectory. 25-year follow-up data on 2833 racially diverse individuals (followed from the mean age of 25.0 years to 50.1 years) from the Coronary Artery Risk Development in Young Adults (CARDIA) prospective observational cohort were analyzed. Participants self-reported their physical activity patterns at eight timepoints over 25 years and were categorized as either moderate physical activity (MPA) or vigorous physical activity (VPA). Noncontrast computed tomography (CT) measured liver fat at the 25-year mark and liver attenuation was measured (where NAFLD is defined as less than 51 hounsfield units, with moderate-severe NAFLD being less than or equal to 40 hounsfield units). Three MPA trajectories were identified: low stable, low increasing, and moderate increasing MPA. Three VPA trajectories were also identified: low stable, moderate decreasing, and high decreasing. The participants who, over 25 years, demonstrated a moderate decreasing or high decreasing VPA pattern were at significantly lower risk for developing NAFLD in middle age (RRModerate VPA 0.74, 95% CI 0.64-0.85; RRHigh VPA 0.59, 95% CI 0.43-0.80) compared to those with low stable VPA over 25 years, even after adjusting for other covariates. The 41% risk reduction of NAFLD in individuals with high decreasing VPA is substantial. Of note, no statistically significant differences in NAFLD risk were noted between the three MPA trajectories. The results of the current study indicate that moderate to high amounts of VPA in early adulthood are associated with lower NAFLD incidence in late adulthood, and that a dose-dependent relationship between exercise intensity and NAFLD risk could exist. Further research should assess the effects of mixed types of physical activity in the life course on relative risk for developing NAFLD, potentially exploring the optimal duration/type of physical activity for reducing NAFLD risk. 

Click to read the study in JAMA Network Open

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