Introduction: Obesity is a disease characterized by excessive accumulation of body fat with health damaging effects. Objective: To assess the impact of two programs for the treatment of grade III obesity, hospitalization and ambulatory care, on weight loss and body composition. Methods: This was a retrospective study based on the analysis of the medical records ofpatients submitted to the above programs between 1990 and2005, with evaluation of weight evolution, body circumferences (abdominal, hip and arm), fat mass (FM, kg) and fat-free mass (FFM, kg). Results: A total of 50 medical records were evaluated, 54% of them concerning patients of the hospitalization program (HP). Both programs were efficient in promoting weight loss, however, it was greater for HP. HP led to reduction of all body circumferences and of FM but its cost was 80 times higher than the ambulatory program. Conclusion: On the basis of the data evaluated, despite its much higher cost, the HP yielded more effective results in terms of weight loss and change of body composition.