Bariatric surgery is the most effective treatment for achieving long-term weight loss in morbidly obese patients. This study investigated prospective changes in gut hormones and metabolic indices after Roux-en-ϒ gastric bypass (RYGB).

Six patients were seen before, and at 1, 3 and 6 months after operation. Blood was collected after a 12-h fast and at regular intervals after a mixed 420-kcal meal. Hormonal responses were determined, and comparisons between basal levels and areas under the curve were made. Visual analogue scores were used to assess satiety, hunger and nausea.

Mean body mass index decreased from 48·3 kg/m² before surgery to 36·4 kg/m² 6 months after RYGB. This was accompanied by a decrease in fasting leptin (P < 0·001) and insulin (P = 0·021) levels. At 1, 3 and 6 months after operation, progressively increasing peptide YY (P < 0·001), enteroglucagon (P = 0·045) and glucagon-like peptide 1 (P = 0·042) responses were observed. There was no change in fasting ghrelin levels (P = 0·144). Postprandial satiety was significantly increased by 1 month after surgery and this was maintained until the end of the study (P < 0·001).

RYGB resulted in substantial weight loss with enhanced postprandial satiety, a sustained weight plateau, and proportionate reduction in fasting insulin and leptin levels. Lack of the expected increase in appetite and food intake as components of a counter-regulatory response may be explained by gut adaptation and the consequent graded rise in the levels of gut hormones that promote satiety.