 The investigators research has demonstrated increased levels of chemical messengers gut hormones released from the gastrointestinal tract after meals in patients who have previously undergone upper gastrointestinal surgery. These chemical messengers play a role in signalling the feeling of fullness during and after a meal satiety. Understanding the mechanisms involved in increased gut hormone secretion after these operations may allow us to use certain medications to block gut hormone release and hence reduce satiety allowing patients to eat more, regain weight and prevent nutritional complications after surgery. 