Inclusion Criteria:  Postmenopausal women (defined as last menses >12 months)  Obesity with a BMI ≥ 35 kg/m², Patients with an indication for bariatric surgery with two surgical techniques, RYGB and SG, but who have never had a bariatric surgery procedure previously, Enrollment will be stratified for each surgical techniques, RYGB and SG, by preoperative diabetes status, defined by having HbA1c >6.5% or a prior physician's diagnosis of diabetes plus use of an antidiabetic medication. Patients who have signed the informed consent.  Exclusion Criteria:  women who were pre- and perimenopausal and men in order to minimize sex hormone and BMA changes unrelated to the surgical procedure. women who used medications known to impact bone metabolism or BMA, including bisphosphonates, teriparatide, denosumab, hormone replacement therapy (HRT) and oral glucocorticoids (>5mg prednisone equivalent daily for>10 days in the last 3 months. Other exclusion criteria included prior bariatric surgery, estimated glomerular filtration rate <30 mL/min, any contraindication to magnetic resonance imagery (MRI).