Taking into account high attrition rates, medium term weight maintenance on Orlistat therapy is markedly reduced. The Cochrane 2003 meta-analysis found high attrition rates ranging from 14% to 52% (average 33%) during the weight loss phase of Orlistat trials. In the XENDOS study, intention to treat analysis which took into account the 48% attrition rate showed a smaller yet significant weight loss with Orlistat (3.6 kg vs 1.4 kg with placebo; P < 0.001) over 4 years (Torgerson et al 2004).
Pharmacoepidemiological studies seem to indicate that attrition rates in clinical practice are even higher (64%–77%) and the major causes of cessation of treatment are high cost and side effects (Vray et al 2005).