OBJECTIVE: To investigate the efficacy of orlistat on the maintenance of weight loss over 3 years following a major weight loss induced by very-low-energy diet (VLED) in obese patients with metabolic risk factors such as dyslipidemia, impaired fasting glucose, and diet-treated type 2 diabetes. RESEARCH DESIGN AND METHODS: Initially, weight loss was induced by an 8-week VLED (600-800 kcal/day) in 383 patients with a mean BMI of 37.5 kg/m(2) (range 30.0-45.2). Those who lost > or = 5% of their body weight (309 of 383 patients) were then randomized to receive lifestyle counseling for 3 years together with either orlistat 120 mg t.i.d. or matching placebo capsules. Primary end points were the maintenance of > or = 5% weight loss after 3 years. Additionally, differences in the development of type 2 diabetes between orlistat and placebo were analyzed. RESULTS: The VLED induced a mean weight loss of 14.4 +/- 2.0 kg among the subsequently randomized patients. The mean weight gain after 3 years was lower with orlistat than with placebo (4.6 +/- 8.6 vs. 7.0 +/- 7.1 kg; P < 0.02). The number of participants who achieved > or =5% weight loss also favored orlistat (67 vs. 56%; P = 0.037). Waist circumference was significantly more reduced in the orlistat group (P < 0.05), but no other differences in the risk factors were observed between the two groups. The incidences of new cases of type 2 diabetes were significantly reduced in the orlistat group (8 cases out of 153 subjects) versus placebo (17 cases out of 156 subjects) (P = 0.041). CONCLUSIONS: The addition of orlistat to lifestyle intervention was associated with maintenance of an extra 2.4 kg weight loss after VLED for up to 3 years in obese subjects. The combination of orlistat and lifestyle intervention was associated with a reduced occurrence of type 2 diabetes.