Heart failure is the leading cause of hospitalization. Obesity is increasingly common and is a major public health problem. The aim of this study is to assess whether obese patients with heart failure can benefit from losing weight via an orlistat-assisted diet. This randomized clinical trial included obese patients with ejection fractions < or =40%. Orlistat and diet counseling were compared with diet counseling alone. Twenty-one consecutive obese patients with heart failure were recruited. Significant improvement in 6-minute walk test (45.8 m; 95% confidence interval, 5.2-86.4 m; p=0.031), functional class (-0.6+/-0.5, p=0.014), weight loss (-8.55 kg; 95% confidence interval, -13.0 to -4.1 kg; p<0.001) and also significant decreases in total cholesterol (p=0.017), low-density lipoprotein cholesterol (p=0.03), and triglycerides (p=0.036) were observed in the orlistat group. Orlistat can promote significant weight loss and symptoms of relief in obese patients with heart failure, as measured by 6-minute walk test and functional capacity. The lipid profile improved. Orlistat was safe and well tolerated.