Orlistat has been well studied in several populations, including patients who do and do not have type 2 diabetes and in patients who have impaired glucose tolerance. Overall, modest, but significant, weight loss was seen in all three groups of patients with favorable effects on the comorbidities of obesity. Orlistat has not been associated with a serious adverse event profile, and the mild GI effects that are seen in some patients are well tolerated. In obese patients who do not have diabetes, weight loss is achieved and maintained as shown in the 2-year studies. Moreover, as was well documented in the Swedish multi-morbidity study, favorable treatment effects on the constituents of the metabolic syndrome are seen. Orlistat, together with a hypocaloric diet, was proven to be effective in preventing diabetes in patients who had impaired glucose tolerance. The addition of orlistat resulted in significant weight loss and significance decreases in levels of HbA1c in patients who had type 2 diabetes who were treated with antihyperglycemic drugs. Studies showed that it is possible to identify early which patients may respond best to treatment. Orlistat offers an attractive treatment option for obese patients who do and do not have diabetes and as a combination drug for treatment of obese patients who have type 2 diabetes.