Objective To study the efficacy of orlistat, as an adjunct to dietary modification, in weight reduction and modification of cardiovascular risk factors in obese patients after 1 year of treatment. Design A total of 3132 obese patients (body mass index 28-43 kg/m(2)) were evaluated in an analysis of pooled data from five randomized, double-blind, placebo-controlled trials of orlistat in conjunction with a hypocaloric diet. Ail studies included a 4-week, single-blind, placebo lead-in period during which patients followed a mildly hypocaloric diet, after which they were randomized to double-blind treatment with orlistat 120 mg three times a day (tid) or placebo for 1 year. Results After 1 year, orlistat 120 mg tid produced significantly more weight loss than placebo (9.2% vs 5.8%; P< 0.001). Furthermore, a greater proportion of orlistat-treated patients lost >5% or >10% of their initial body weight compared to placebo (69.6% vs 51.9%; P< 0.001 and 42.1% vs 22.7%; P< 0.001, respectively). Improvements in cardiovascular risk factors were observed during a 4-week placebo lead-in period. However, following randomization, orlistat-treated patients had significantly greater improvements than placebo-treated patients in several lipid parameters including total cholesterol, low-density lipoprotein-cholesterol, triglycerides, and apolipoprotein B. In addition, orlistat had a beneficial effect on oral glucose tolerance tests status, waist circumference and systolic and diastolic blood pressure. Orlistat was well tolerated and had a similar safety profile to placebo. I Hypertens 1998, 16:2013-2017 (C) 1998 Lippincott Williams & Wilkins.