Bone Metabolism After Laparoscopic Gastric Bypass Surgery (BABS)

Obese female and male adult patients eligible for laparoscopic gastric bypass surgery according to the national Austrian guidelines will be included in this study upon request and after patient approval.

Baseline data collection and quarterly follow up visits are planned to investigate the changes in bone mineral density and body composition measured by dual energy X-ray absorptiometry as well as the evaluation of serum bone turnover markers of bone formation and resorption.

After surgery subjects will be randomized into two groups:

Daily oral calcium (500mg) and weekly vitamin D3 supplementation (16.000 IU calciferol)or no supplementation of calcium and calciferol.

A sub-study (approximately 15% of study population) with transiliac bone biopsies will also be performed to investigate histomorphometric and histologic changes in bone (biopsy baseline and after 24 months).

The planned duration of the study is 24 months for each subject. Serum bone turnover markers will be collected every 3 months, dual energy X-ray absorptiometry measurements will be performed every 6 months.

Inclusion criteria

• body mass index >35
• female and male patients
• age 18 - 65 years
• eligible for laparoscopic gastric bypass surgery according to the Austrian national guidelines

Exclusion criteria

• any history of malignancy except basalioma
• any prior antiresorptive treatment
• any prior calcium or vitamin D supplementation
• any secondary disease affecting bone metabolism