Effect of Roux-en Y Gastric Bypass on Bone Metabolism in Patients with Morbid Obesity: Mansoura Experiences

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Roux-en-Y gastric bypass (RYGBP) has been found to be the most efficient way to lose weight and maintain the weight loss in morbid obesity. However, with the formation of a new stomach and the modification of intestinal anatomy, there are significant changes on bone metabolism. The objectives of this study were to evaluate effects of weight loss on bone metabolism after Roux-en Y gastric bypass in patients with morbid obesity.


Our study included 70 patients with morbid obesity; RYGB was done for all patients. Daily postoperative oral supplementation with 1,000 mg of calcium and 800 IU of vitamin D was done for each patient. Body weight (BW), body mass index (BMI), total body fat, total lean tissue mass, bone mineral content (BMC), bone mineral density (BMD), total bone area (TBA; using dual energy X-ray absorptiometry), serum calcium, parathyroid hormone (PTH), 25-OH vitamin D, 24-h urinary calcium, and bone-specific alkaline phosphatase (BSAP) were assessed preoperatively and 1 year after surgery.


In our study, females comprised 70% of cases. The mean age was 35 ± 8.8 years. One year after RYGB, BW decreased significantly from 132.8 ± 26.5 to 90.3 ± 17.3 kg (p = 0.001). BMI decreased significantly from 48 ± 7.3 to 32.6 ± 4.1 kg/m2 (p = 0.001). BMC decreased significantly from 2,968.6 ± 71.4 to 2,700.8 ± 45.4 g (p = 0.001). BMD decreased significantly from 1.026 ± 0.03 to 1.22 ± 0.015 g/cm2 (p = 0.001). TBA decreased significantly from 2,356.2 ± 35.4 to 2,216.3 ± 43.5 cm2 (p = 0.001). Serum calcium, 24-h urinary calcium, and BSAP were not significantly decreased while 25-OH vitamin D and PTH were not significantly increased after surgery.


From this study, it is shown that RYGBP operation gives very good results as regards reduction of body weight in morbidly obese patients. Postoperative supplementation with calcium and vitamin D partially corrects osteoporosis. Thus, these patients need periodic follow-up for BMD, PTH, calcium, serum vitamin D, and markers of bone resorption and formation specially postmenopausal female.

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