ObjectiveAttrition rates of up to 77% have been reported in conservative weight-reduction programs for the treatment of obesity. In view of the cost of such programs to the health system, there is a need to identify the variables that predict premature discontinuation of treatment. Previous studies have focused mainly on somatic and sociodemographic parameters. The prospective influence of psychological factors has not been systematically investigated to date.MethodsA total of 164 patients (138 of whom were women) with a mean age of 45 years and a mean body mass index of 39.57 participated in a 1-year outpatient weight-reduction program at the Charité – Universitätsmedizin Berlin University Hospital. The program included movement therapy, dietary advice, psychoeducational and behavioral interventions, relaxation procedures, and consultations with a specialist in internal medicine and a psychologist. Patients also underwent regular laboratory and psychological testing. The results were evaluated using a t-test, χ2-test, and logistic regression analysis.ResultsSeventy-one of the 164 patients (61 women, mean age = 43 years, mean body mass index = 39.53) withdrew before the end of the program (attrition rate = 43.3%). While there were no differences between the somatic and metabolic characteristics of those who withdrew and those who remained, the sociodemographic and psychological factors had some relevance. In particular, “expectation of self-efficacy” (Fragebogen zu Selbstwirksamkeit, Optimismus und Pessimismus [SWOP]), “not working,” “tiredness” (Berliner Stimmungsfragebogen [BSF]), “pessimism” (SWOP) and “positive reframing” (Brief-COPE) were found to play a role in whether participants subsequently dropped out of the treatment. “Support coping” (Brief-COPE) and “older age” prior to the start of treatment were identified as variables that promoted treatment adherence.ConclusionThe results are discussed in light of previous findings and with regard to whether the modules of the weight-reduction program should be adapted.