Exercise Dose and Nonalcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) affects about 20% 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 two levels of aerobic
exercise on: 1) hepatic fat content; 2) hepatic lipoprotein kinetics; 3) insulin
sensitivity; 4) plasma inflammatory markers; and 5) potential cellular mechanism that
regulate insulin action and inflammation. We hypothesize that aerobic exercise will
decrease hepatic fat content, improve hepatic, skeletal muscle, and adipose tissue insulin
sensitivity, 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 (> 5% hepatic fat content) to one of three groups: Group 1 (Control, no
exercise), Group 2 (Low-Dose Aerobic Exercise- 150 min/wk of supervised exercise performed
at 45-55% of O2 max), and Group 3 (Moderate-Dose Aerobic Exercise - 300min/wk of supervised
exercise performed at 45-55% of O2 max) to determine the effects of low and moderate doses
of aerobic exercise.