PURPOSE: To characterize the comorbidities associated with hospitalizations for obesity and the relationship of these co-morbidities with bariatric surgery and hospitalization costs during the period between 2000 and 2010 in Sao Paulo that were financed by the Brazilian Public Health System (SUS). METHODS: We used data from the Hospital Information System of the Unified Health System (SIH-SUS) for selected individuals hospitalized for obesity according to International Classification of Diseases (ICD10). RESULTS: The total cost of hospitalizations was approximately two million dollars, with 67% of the total cost for bariatric and reconstructive surgery. Women accounted for 87% of hospitalizations, and 77% of subjects were aged between 30 and 59 years; the main comorbidity found was hypertension, and the procedures performed were bariatric surgery and reconstructive surgery (post-bariatric surgery). CONCLUSION: Obesity is a major public health problem that affects people of productive age, causing high costs of hospitalization, which reinforces the requirement for preventive interventions beginning from childhood.