Effects of Gastric Bypass Surgery and Calcium Metabolism and the Skeleton

Overview

Obesity is a chronic illness of staggering proportions. Because weight loss through diet and exercise is difficult to attain and maintain, there has been escalating interest in bariatric surgery, including Roux-en-Y gastric bypass. Gastric bypass surgery results in long-term weight loss, dramatic improvement in comorbidities such as diabetes, and decreased mortality. Emerging evidence suggests, however, that gastric bypass may have negative effects on bone health. Because of the serious consequences of osteoporosis and fracture, this is of great concern. This study of the effects of gastric bypass on calcium metabolism and the skeleton may positively impact the clinical care of gastric bypass patients by their surgeons, primary care providers, and endocrinologists. Further, the knowledge gained may inform future investigation into the relationships between obesity, weight loss, and bone biology.

Full Title of Study: “Effects of Gastric Bypass Surgery on Calcium Metabolism and the Skeleton”

Study Type

  • Study Type: Observational
  • Study Design
    • Time Perspective: Prospective
  • Study Primary Completion Date: April 2014

Arms, Groups and Cohorts

  • Gastric Bypass Surgery Patients
    • Obese men and women undergoing gastric bypass surgery

Clinical Trial Outcome Measures

Primary Measures

  • Change in Intestinal Calcium Absorption
    • Time Frame: 6 months (between baseline and 6 months)
    • Change in fractional calcium absorption, determined by dual stable isotope method. Fractional calcium absorption is the fraction of ingested calcium that is absorbed, which is expressed here as the percentage of ingested calcium that is absorbed. The 6-month change is the mean difference in percentage absorption between time points. For example, if fractional calcium absorption were to decrease from 30% preoperatively to 25% at the 6-month postoperative time point, the change in fractional calcium absorption would be -5%.

Secondary Measures

  • Areal Bone Mineral Density (BMD) at the Femoral Neck
    • Time Frame: 12 months post-operatively (between baseline and 12 months)
    • Areal BMD at the femoral neck by dual-energy X-ray absorptiometry (DXA). The 12-month change is the percentage change between the 12 month and baseline time points.
  • Trabecular Number at the Tibia
    • Time Frame: 12 months post-operatively (between baseline and 12 months)
    • Trabecular number at the tibia by high-resolution peripheral quantitative computed tomography (HR-pQCT). The 12-month change is the percentage change between the 12 month and baseline time points. HR-pQCT images were analyzed using the manufacturer’s standard clinical evaluation protocol, with trabecular structure extracted using a threshold-based binarization process.

Participating in This Clinical Trial

Inclusion Criteria

Scheduled to undergo gastric bypass surgery. Please note that to be eligible, one must already be working with a bariatric surgeon and with plans in place to undergo gastric bypass. This study is unable to arrange or pay for gastric bypass surgery. Exclusion Criteria:

  • Perimenopausal women – Known intestinal malabsorption – Prior bariatric surgery – Use of medications known to impact bone and mineral metabolism – Disease known to affect bone – Illicit drug use or alcohol use >3 drinks/day – Serum calcium >10.2 mg/dL – Calculated creatinine clearance <30 mL/min – Weight >350 pounds – Wrist circumference >12 inches or calf circumference >17 inches

Gender Eligibility: All

Minimum Age: 25 Years

Maximum Age: 70 Years

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • VA Office of Research and Development
  • Provider of Information About this Clinical Study
    • Sponsor
  • Overall Official(s)
    • Anne L Schafer, MD, Principal Investigator, San Francisco VA Medical Center, San Francisco, CA

Citations Reporting on Results

Schafer AL, Weaver CM, Black DM, Wheeler AL, Chang H, Szefc GV, Stewart L, Rogers SJ, Carter JT, Posselt AM, Shoback DM, Sellmeyer DE. Intestinal Calcium Absorption Decreases Dramatically After Gastric Bypass Surgery Despite Optimization of Vitamin D Status. J Bone Miner Res. 2015 Aug;30(8):1377-85. doi: 10.1002/jbmr.2467. Epub 2015 May 21.

Schafer AL, Li X, Schwartz AV, Tufts LS, Wheeler AL, Grunfeld C, Stewart L, Rogers SJ, Carter JT, Posselt AM, Black DM, Shoback DM. Changes in vertebral bone marrow fat and bone mass after gastric bypass surgery: A pilot study. Bone. 2015 May;74:140-5. doi: 10.1016/j.bone.2015.01.010. Epub 2015 Jan 17.

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