Exercise Dose and Nonalcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) affects about 33% of adults in the United States. The prevalence of NAFLD is four to five times higher in obese than lean persons and is associated with insulin resistance and the metabolic syndrome. Decreasing calorie intake and increasing physical activity has been recommended as primary therapy for NAFLD, but the independent effect of aerobic exercise is unknown. The current exercise guidelines for disease prevention and weight management range from 150 min/wk, recommended by the Centers for Disease Control and the American College of Sports Medicine, to 300 min/wk, recommended by the Institute of Medicine. However, it is not known whether aerobic exercise alone can improve NAFLD, and which recommended dose of exercise might have the most beneficial effects. The purpose of this proposal is to determine the effect of moderate intensity endurance exercise on: 1) hepatic fat content; 2) hepatic lipoprotein kinetics; and 3) plasma inflammatory markers. We hypothesize that aerobic exercise will decrease hepatic fat content, improve VLDL kinetics, and decrease inflammation in a dose-dependent fashion. The results from this study will help determine exercise guidelines for obese patients with NAFLD, and lay the groundwork for future studies evaluating the effects of exercise on metabolic diseases associated with obesity. This proposal involves conducting a randomized controlled trial that will randomize obese subjects with NAFLD (\> 10% hepatic fat content) to one of two groups: Group 1 (Control, no exercise) and Group 2 (Moderate Intensity Aerobic Exercise- 150 min/wk to 300 min/wk of supervised exercise performed at 45-55% of O2 max).