[What is the evidence with regard to the effectiveness of orlistat?]

Obesity is worldwide one of today's most important medical and public health problems. Orlistat (Xenical) is a relatively new drug in the pharmacological treatment of obesity which partially blocks fat absorption. The following article analyses the available evidence of orlistat's effectiveness in the treatment of obese patients.

Three randomised controlled trials investigating the effect of orlistat in the treatment of obesity were identified by systematic Medline search. The internal and external validity of these studies was assessed using systematic criteria.

All three studies consistently demonstrate a treatment benefit of orlistat compared to placebo. Patients treated with orlistat lost an average of 3.4 kg more than patients taking placebo while on a hypocaloric diet. Simultaneously, control of cardiovascular risk factors improved independently of the observed weight loss. Up to 40% of all patients experienced gastrointestinal side effects which were generally well tolerated. The studies prove 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 studies' internal and external validity.

Based on these studies orlistat is an efficient pharmacological treatment for obesity in patients adhering to a hypocaloric diet. Studies demonstrating orlistat's effectiveness in a primary care setting are so far lacking. From a public health perspective there is a need for a randomised controlled trial showing not only orlistat's effectiveness on surrogate markers in a primary care setting but, ideally, a reduction in obesity-related mortality and morbidity.