Objective: Structured obesity treatment programs at primary care level are becoming increasingly important. However, evidence from current treatment approaches in the long term is lacking. In view of this fact we evaluated a standardized, meal replacement-based weight loss program (myLINE®; AENGUS, Graz, Austria) according to the currently applicable guidelines. Methods: Data of overweight and obese individuals (n = 70) who participated at least 36 months in the program were analyzed. Data were collected at baseline (T0) as well as after 1, 3, 6, 12, 24, and 36 (T1-T36) months. Body composition was measured by conventional anthropometry and bioelectrical impedance analysis. Results: Compared to T0, a maximum weight, BMI, fat mass, absolute body cell mass (BCM) reduction and an increase of relative BCM could be seen at T6. Subsequently, the findings reveal a significant reduction of body weight and body fat and a satisfying development of body cell mass during the observation period of 36 months. Conclusion: The evaluated program complies with national and international guidelines for the therapy of obesity in adults and is efficient and meaningful for a long-term therapeutic use in primary care..