What is the evidence for the effectiveness of orlistat?

Background: Obesity is worldwide one of today's most important medical and public health problems. Orlistat (Xenical(R)) is a relatively new drug in t he pharmacological treatment of obesity which partially blocks fat absorpti on. The following article analyses the available evidence of orlistat's eff ectiveness in the treatment of obese patients. Methods: Three randomised controlled trials investigating the effect of orl istat in the treatment of obesity were identified by systematic Medline sea rch. The internal and external validity of these studies was assessed using systematic criteria. Results: All three studies consistently demonstrate a treatment benefit of orlistat compared to placebo. Patients treated with orlistat lost an averag e of 3.4 kg more than patients taking placebo while on a hypocaloric diet. Simultaneously, control of cardiovascular risk factors improved independent ly of the observed weight loss. Up to 40% of all patients experienced gastr ointestinal side effects which were generally well tolerated. The studies p rove that treatment with orlistat can result in a moderate weight reduction . However, the results of the studies cannot be easily generalised to obese patients in a primary care setting, due to limitations concerning the stud ies' internal and external validity. Conclusions: Based on these studies orlistat is an efficient pharmacologica l treatment for obesity in patients adhering to a hypocaloric diet. Studies demonstrating orlistat's effectiveness in a primary care setting are so fa r lacking. From a public health perspective there is a need for a randomise d controlled trial showing not only orlistat's effectiveness on surrogate m arkers in a primary care setting but, ideally, a reduction in obesity-relat ed mortality and morbidity.