The effect of sibutramine on energy expenditure and appetite during chronic treatment without dietary restriction

OBJECTIVE: To assess the contribution of a thermogenic effect to weight loss induced by eight weeks treatment with sibutramine (15mg/d) vs placebo in obese subjects. DESIGN: Randomised, placebo controlled, double blind study. SUBJECTS: Thirty-two (7 male, 25 female) healthy obese body mass index (BMI) 33.9 +/- 0.5 kg/m(2) subjects completed the trial. MEASUREMENTS: Energy expenditure (EE) was measured by indirect calorimetry during a 32 h stay in a respiration chamber before and after 8 weeks treatment. Visual analogue scales were completed for assessment of appetite sensation. No dietary restriction was given. RESULTS: Sibutramine caused a significant weight loss compared with placebo (-2.4 kg vs + 0.3 kg, P < 0.001). Despite the larger weight loss after 8 weeks, 24-h EE did not decrease more in the sibutramine than in the placebo group (-2.6% vs -2.5%, P = ns). When the changes in 24-h EE were adjusted for changes in body weight, 24-h EE decreased significantly less in the sibutramine group than in the placebo group (0.8% vs 3.8%, P < 0.02). Sibutramine significantly decreased both hunger and anticipated food consumption, and increased satiety scores. CONCLUSIONS: The weight reducing effect of sibutramine in humans is caused by a dual mechanism: reduction of energy intake by increasing satiety and decreasing hunger and prevention of the decline in EE that follows weight loss.