CRD summary: This review assessed the effects of orlistat on weight loss in overweight patients. The authors concluded that orlistat is effective in improving both weight loss and serum lipid profiles in obese patients at low and high cardiovascular disease risk, and in obese patients with type 2 diabetes. The authors' conclusions are appropriate and appear reliable.

CRD commentary: The review question was clearly defined in terms of the intervention, participants, outcomes and study designs. Only two databases were searched to identify relevant studies, and no efforts were made to locate unpublished material; funnel plots did suggest the possibility of of publication bias. However, efforts were made to minimise language bias. Two reviewers were involved in selecting studies for inclusion in the review. The authors did not report how many reviewers were involved in the validity assessment and data extraction processes, thus it is not known whether any efforts were made to minimise reviewer bias and errors. The quality of the primary studies was assessed. The use of a random-effects meta-analysis to combine the studies seemed appropriate, and both statistical and clinical differences between the studies were explored. The authors mentioned in their discussion that several studies had high drop-out rates (30 to 40% with orlistat and 10 to 20% with placebo), but did not mention the use (or lack of use) of an intention-to-treat analysis or the influence of drop-outs on the results. Overall, the authors' conclusions are appropriate and appear reliable.