Background: Bariatric surgery promotes changes in body composition, that can include the loss of bone mineral density (BMD). There is a lack of studies on the evolution of bone health of elderly people who underwent bariatric surgery, in general, and when comparing the gastric bypass (GB) and sleeve gastrectomy (SG) techniques. Objective: To evaluate the bone health of elderly patients with obesity undergoing bariatric surgery. Methods: This is a prospective randomized clinical study, that was carried out with individuals of both sexes, ≥65 years, undergoing GB or SG and who met the inclusion criteria. Age, gender and comorbidities (type 2 diabetes mellitus, arterial hypertension, dyslipidemia and osteoarthrosis) were collected and analyzed at baseline. Anthropometric data (weight, body mass index, percentage of weight loss, percentage of excess weight loss), laboratory tests related to bone health and bone mineral density were analyzed before and 24 months after surgery. Results: A total of 36 patients (GB, n=18; SG, n=18) were evaluated. At baseline, except for sex and preoperative body mass index, which was higher in GB, groups were similar. After 24 months, GB was superior for weight loss (%WL) and excess weight loss (%EWL). Regarding bone health, a significant decrease of BMD was observed in the spine, total proximal femur and femoral neck in all groups, with an average decrease of 5.1%, 10.5% and 15.1%, respectively. In addition, the observed decrease in BMD was up to 25% in the total femur after 24 months, six patients went from normal BMD to osteopenia and one from osteopenia to osteoporosis. There was no difference in parathormone values. However, there was an association between the increase in parathormone and the decrease in BMD in the spine, mainly in the GB group. There was no association between %WL and %EWL with the reduction in BMD. Conclusion: Bariatric surgery was related to the reduction of BMD in elderly patients, but there was no statistical difference between the two surgical techniques.
