This is a randomized, controlled, double blind clinical trial. The purpose of this study is to investigate the weight loss efficacy of entacapone. In this study, participants are randomly divided into entacapone and placebo groups. The percentage change in body weight, the body mass index, waist circumstance, extent of fatty liver, quantity of visceral fat, serum insulin, serum triglyceride and the adverse effects are compared between the two groups.