 All subjects will undergo a total of 3 OGTTs, 1 before surgery and 2 after. The OPEN group will also have a glucose tolerance test via a gastrostomy tube GGTT placed in the duodenum per routine surgical procedure as described below. The OGTT consists of a 12-hour overnight fast followed by drinking a 225 ml of solution containing 75 grams of a glucose Glucola, over 30 minutes. 30 minutes is the average time a patient requires in order to drink a 225ml Glucola drink after gastric bypass surgery. In order to be able to make a valid comparison of the three OGTTs, each OGTT will require that the subject drink over 30 minutes. Blood samples are obtained from an intravenous catheter at various time intervals: 5 minutes and immediately before drinking the Glucola, and 5, 10, 15, 30, 60, 90, 120, and 180 minutes afterwards. Blood levels of glucose, insulin, glucose-dependent insulinotropic polypeptide GIP, glucagon, and Glucagon-Like Peptide GLP-1, CCK, ghrelin and c-peptide will be determined from the samples obtained. In addition, at hour 2 during the OGTT when glucose peaks we will obtain a real-time glucose level with a drop of blood from the indwelling line. The GGTT follows that same protocol as the OGTT, but the Glucola is administered via a gastrostomy tube, placed per routine surgical procedure in patients undergoing open GBS. Approximately 1 week before surgery, all subjects will undergo an OGTT in the GCRC. Between day 6 and 10 after their surgery, when subjects are tolerating their standard 240cc liquid meals 3-4 times daily, subjects will undergo the third OGTT. Although most subjects are discharged on day 3 or 4 after surgery, and will be asked to return to the GCRC, those subjects who remain in the hospital through day 5 will have the option to remain in the hospital for an additional time 1-2 days or to go home and return to the GCRC within 5 days no later than POD 10 The additional hospital days will be paid for by the GCRC. After surgery, subjects in LAP group will have one OGTT. Subjects in the OPEN group will have a GGTT on one day and an OGTT on the following day. Subjects will be weighed before surgery and every day during the first week after surgery and before each glucose tolerance test. All subjects will undergo a final OGTT approximately 3 -4 weeks after surgery. This will take place in the GCRC on the same day as a routine follow up visit to their surgeon. 