Effects of Bariatric Surgery on Insulin

This study, conducted at the NIH Clinical Research Unit (CRU) at the Phoenix Indian Medical Center, will compare the effects of two methods of bariatric surgery, the adjustable BAND and Roux-en-Y gastric bypass, on insulin. Bariatric surgery is a treatment for achieving and maintaining weight loss. The study will look at how this surgery might improve how insulin (a hormone important for regulating blood sugar levels) is made and works in the body and the possible role of changes in other hormones produced by the gut (stomach and intestines). People between 18 and 50 years of age who are scheduled to have either laparoscopic adjustable BAND or Roux-en-Y gastric bypass surgery may be eligible for this study. Candidates are screened about 4 to 6 weeks before their surgery with a medical history, blood tests and an oral glucose tolerance test for diabetes. Participants spend 4 days at the CRU or 2 days overnight and an out-patient visit approximately 4 to 6 weeks before their surgery and again 3 to 6 weeks after their surgery. They return for a 4-6 hour visit at the CRU at 6 months, 1 and 2 years after surgery and for half-day outpatient visits at 3, 4 and 5 years after surgery for the following procedures: * Blood and urine tests, including a pregnancy test for women. (4-day and 2-day admissions and years, 3, 4 and 5) * DEXA, an x-ray scan to determine body fat content. (4-day and 2-day admissions and years, 3, 4 and 5) * MRI scan to measure fat tissue in the abdomen. (4-day and 2-day admissions and years, 3, 4 and 5) * Intravenous (I.V.) glucose tolerance test for risk of obesity and diabetes. A sugar solution is given through a needle in a vein of one arm and blood samples are drawn through another needle in a vein in the other arm. (4-day admissions) * Meal test to measure blood sugar and insulin and gut hormone levels after a meal. After an I.V. line is placed in an arm vein, the subject eats breakfast over 20 minutes. Blood samples are collected halfway throug