 20 patients in each group will undergo more detailed measurements of food intake, hunger, satiety, gut hormones and bile acids. The research protocol will be the similar to that previously published by the Department of Metabolic Medicine, Imperial College, London. Participants will be fasted for 12 hours overnight and will attend for the study on 5 occasions. On each occasion venous blood samples will be taken and visual analogue scores will be measured over a 3 hour period using previously published methodology Samples or sample containers will be anonymised before collection but will be traceable back to the individual patients. Urine will be collected once. A qualified medical doctor will insert a venepuncture cannula into the arm of the patient and 5ml blood will be withdrawn at baseline, 15, 30, 60, 90, 120, 150 and 180 minutes following ingestion of a standard 400kcal meal as below. 