Effects of Gastric Bypass Surgery and Calcium Metabolism and the Skeleton

VA Office of Research and Development55 enrolled

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.

Study Type

OBSERVATIONAL

Enrollment

Conditions

Obesity, Morbid Gastric Bypass

Eligibility

Sex: ALLMin age: 25 YearsMax age: 70 Years

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

Change in Intestinal Calcium Absorption

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%.

Time frame: 6 months (between baseline and 6 months)

Secondary Outcomes

Areal Bone Mineral Density (BMD) at the Femoral Neck

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.

Time frame: 12 months post-operatively (between baseline and 12 months)

Trabecular Number at the Tibia

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.