Nine trials (1,829 participants, range 24 to 539) were included in the review: six trials of sibutramine and three trials of orlistat. The quality of the included studies was variable: four trials scored 5, two trials scored 4, two trials scored 3 and one scored 2.
Weight loss: Three out of four sibutramine trials showed a statistically significantly greater reduction in BMI compared with placebo. Two out of three trials of orlistat showed a statistically significantly greater reduction in BMI compared with placebo. Change in BMI for sibutramine ranged from -1.5 to -3.6kg/m². Change in BMI for orlistat ranged from -0.55 to -4.09 kg/m². Three out of five sibutramine trials showed a statistically significantly greater absolute initial weight change compared with placebo. Two out of two trials of orlistat showed a statistically significantly greater absolute initial weight change compared with placebo after 12 months. Change in initial weight for sibutramine ranged from -2.81 to -10.3kg/m², and change in initial weight for orlistat ranged from +0.53 to -6.27kg/m².
Quality of life: One trial indicated that there was no significant difference between placebo and sibutramine groups; both patient groups showed improvements in quality of life at the end of the study.
Adverse events: Two trials reported similar adverse events between sibutramine and placebo apart from tachycardia, which was higher with sibutramine (13%) compared with placebo (6%). Other side-effects associated with sibutramine were dry mouth, constipation, dizziness, insomnia and hypertension, all with a frequency of less than 12%. The most common adverse effects associated with orlistat were gastrointestinal, mostly mild to moderate.