OBJECTIVES: This study was to estimate economic burden of obesity and to assess the impact of bariatric surgery on health care costs and utilization in adults in Alberta.  METHODS: Multivariate regression models were developed to estimate the impact of BMI on physician, outpatient and inpatient costs and visits. A pre-post analysis over a 5-year period was conducted to compare the cost and visits before and after surgery. Patients who received bariatric surgery in 2006 were identified using the the Canadian Classification of Health Interventions (CCI) codes that correspond to bariatric surgery. Total physician, inpatient and outpatient costs and visits were calculated across all patients, over a period of two years before and two years after surgery. Health utilization data from Alberta provincial health administrative databases were linked with epidemiologic and demographic data contained in Canadian Community Health Survey (CCHS).  RESULTS: When combining physician and outpatient costs, the mean estimate per obese resident was $696, following by $545 for overweight, $523 for underweight, and $480 for normal weight residents. Compared to normal weight, obesity, overweight and underweight were associated with increases of $217, $65 and $44, respectively. There were 217 bariatric surgery recipients in 2006. Health care costs and utilization two years pre-surgery were greater than two years post-surgery.  The marginal change in health care costs and utilization between 2004 and 2005, however, was positive, indicating an increase prior to surgery. In contrast, the marginal change in health care costs and utilization was negative, indicating a decrease post-surgery. The estimate of total physician and hospital costs associated with bariatric surgery was $12,175.79 (SE: $586.75). CONCLUSIONS: Obesity placed a large economic burden on health care system. The bariatric surgery may alter the upward trajectory of health utilization for severely obese patients. Further research including longer follow-up period is necessary to confirm the impact of bariatric surgery.