To prospectively evaluate the amount of weight loss and subsequent maintenance and to identify correlates of successful weight reduction in overweight and obese outpatients treated in a specialized health care center.

A treatment program involving diet, exercise and behavior modification was provided in an outpatient setting. Twenty-four treatment courses with a total of 177 participants (age: 45.5±12.2 year; BMI: 36.7±5.6kg/m²) were run.

Weight and baseline characteristics were recorded at start of program; weight was re-assessed at the end of treatment and 1 year after the end of treatment.

Patients achieved a significant weight loss of 5.6±7.9kg (5.1±6.4% of initial body weight) in the course of 1 year. An average of 80.8% or 4.8kg of initial weight loss was maintained a year after treatment, representing a significant weight regain. A higher initial BMI, intake of venlafaxin, a higher percentage of course attendance, course completion and hypertension were associated with greater weight loss. The interaction of the specific treatment course and the percentage of attendance explained 25% of the variance of percental total weight loss.

Significant weight losses can be achieved by overweight and obese patients after a treatment program in specialized health care addressing diet, exercise and behavioral aspects. Weight loss maintenance remains difficult for patients. The specific treatment group itself and attendance of course sessions are critical for weight loss and should be considered in the design and evaluation of group-based treatment programs.