OBJECTIVE: To examine the effect of orlistat (XenicalÔ) treatment on body composition and resting energy expenditure (REE) during a 2 y weight-reduction programme in obese Finns. SUBJECTS: Of initially 96 obese subjects who participated in the weight-reduction programme, those 72 subjects (13 men, 59 women, body mass index (BMI) 35.9±3.9 kg/m2, age 43.4±6.0 y, mean±s.d.) with the complete set of data for 2 y were included in the study. DESIGN: After a 4-week lead-in period, subjects were randomized with either orlistat 120 mg t.i.d. or placebo t.i.d. in conjunction with a mildly hypoenergetic balanced diet for 1 y. This was followed by 1 y double-blind period with the subjects within each treatment group re-assigned to receive orlistat 120 mg t.i.d. or placebo t.i.d. in conjunction with a weight maintenance diet. MEASUREMENTS: Body composition and REE were measured after an overnight fast by a bioelectrical impedance method and indirect calorimeter, respectively. The measurements were performed at the beginning and at 3, 6, 12 and 24 months. RESULTS: During the first year, the orlistat-treated group had greater reduction of body weight and fat mass but not of fat-free mass or REE as compared to placebo. During the second year, orlistat treatment was associated with smaller regain of body weight and fat mass with no significant differences in the changes of fat-free mass or REE as compared to placebo. CONCLUSION: In addition to better weight loss and maintenance of reduced weight, orlistat treatment is associated with beneficial changes in body composition but with no excess decrease in resting energy expenditure as compared to that achieved during placebo with a dietary therapy alone. International Journal of Obesity (2000) 24, 1567-1572 | 
