 Both diets will be 1170-1870 kcalday, consisting of 36 CHO, 26.2 protein, and 37.6 fat. The MCT diet will contain 30.2 of total calories at MCT oil. The percentages given are based on the shake and oil consumption only 1170 kcalday. The remainder of the diet will vary according to patients selections from the list of permitted foods, up to an additional 700 kcalday for the total 1870 kcalday. Subjects will receive a multi-vitamin each day. Subjects will also receive two Fibercon capsules per day to prevent possible bowel changes associated with being on a full liquid diet. It is estimated patients will lose between 10 and 30 pounds before surgery. This is a standard of care as all patients are encouraged to lose this amount prior to surgery. This small amount of weight loss from initial body weight is considered beneficial in reducing complications of gastric bypass surgery in morbidly obese patients with significant co-morbidities. 