IMPORTANCE Nonalcoholic fatty liver disease (NAFLD) is a prevalent risk factor for chronic liver disease and cardiovascular disease. OBJECTIVE To compare the effects of moderate and vigorous exercise on intrahepatic triglyceride content and metabolic risk factors among patients with NAFLD. DESIGN, SETTING, AND PARTICIPANTS In this randomized clinical trial, participants with central obesity and NAFLD were recruited from community-based screening in Xiamen, China, from December 1, 2011, through December 25, 2013. Data analysis was performed from August 28, 2015, through December 15, 2015. INTERVENTIONS Participants were randomly assigned to vigorous-moderate exercise (jogging 150 minutes per week at 65%-80% of maximum heart rate for 6 months and brisk walking 150 minutes per week at 45%-55% of maximum heart rate for another 6 months), moderate exercise (brisk walking 150 minutes per week for 12 months), or no exercise. MAIN OUTCOMES AND MEASURES Primary outcome, change in intrahepatic triglyceride content measured by proton magnetic resonance spectroscopy at 6 and 12 months; secondary outcomes, changes in body weight, waist circumference, body fat, and metabolic risk factors. RESULTS A total of 220 individuals (mean [SD] age, 53.9 [7.1] years; 149 woman [67.7%]) were randomly assigned to control (n = 74), moderate exercise (n = 73), and vigorous-moderate exercise (n = 73) groups. Of them, 211 (95.9%) completed the 6-month follow-up visit; 208 (94.5%) completed the 12-month follow-up visit. Intrahepatic triglyceride content was reduced by 5.0%(95% CI, -7.2% to 2.8%; P < .001) in the vigorous-moderate exercise group and 4.2% (95% CI, -6.3% to -2.0%; P < .001) in the moderate exercise group compared with the control group at the 6-month assessment. It was reduced by 3.9%(95% CI, -6.0% to -1.7%; P < .001) in the vigorous-moderate exercise group and 3.5%(95% CI, -5.6% to -1.3%; P = .002) in the moderate exercise group compared with the control group at the 12-month assessment. Changes in intrahepatic triglyceride content were not significantly different between vigorous-moderate and moderate exercise at the 6- or 12-month assessment. Body weight, waist circumference, and blood pressure were significantly reduced in the vigorous-moderate exercise group compared with the moderate exercise and control groups at the 6- month assessment and in the vigorous-moderate and moderate exercise groups compared with the control group at the 12-month assessment. In addition, body fat was significantly reduced in the vigorous-moderate exercise group compared with the moderate exercise and control groups at the 12-month assessment. After adjusting for weight loss, the net changes in intrahepatic triglyceride content were diminished and became nonsignificant between the exercise and control groups (except for the moderate exercise group at the 6- month assessment). CONCLUSIONS AND RELEVANCE Vigorous and moderate exercise were equally effective in reducing intrahepatic triglyceride content; the effect appeared to be largely mediated by weight loss.