Impact of posture and meal volume on gastric emptying and gut hormones after Roux-en-Y gastric bypass (RYGB)

Effects of posture and meal volume on gastric emptying, gut hormones, glycaemia, plasma insulin, haemodynamics, absorption, appetite, and gastrointestinal symptoms after gastric bypass. Gastric emptying will be measured using scintigraphy for 4 hours directly after meal consumption Gut hormones, glycaemia, plasma insulin and glucose absorption will be measured by taking blood samples at baseline (before meal consumption), and throughout the 4 hour duration of the study (after meal consumption) with the last sample taken at 240mins. Appetite and gastrointestinal symptoms will be measured using questionnaires filled out at baseline and throughout the study with the last questionnaire filled out at the completion of the study (240mins) Each subject will undergo concurrent measurements of gastric emptying, gut hormones, blood glucose, blood pressure, heart rate and gastrointestinal symptoms on 4 occasions, separated by at least 4 weeks in randomised order: (i) sitting & 50ml water/50g glucose; (ii) sitting & 200ml water/50g glucose; (iii) supine & 50ml water/50g glucose; and (iv) supine & 200ml water/50g glucose.