Contribution of the level of protein load and duration, to the effects of small intestinal protein, on gut motility, gut hormone release and sensations of appetite.

INTERVENTION: A single 60 minute intraduodenal infusion at 4mL/min of: a) 0 kcal/min (control of saline solution ) b) 0.5 kcal/min (Whey Protein Hydrolysate) c) 1.5 kcal/min (Whey Protein Hydrolysate) d) 3.0 kcal/min (Whey Protein Hydrolysate) Appetite sensation questionnaires in the form of a Visual Analogue Scale (VAS), blood samples. A buffet meal will be provided at the end of infusion and the participant has 30 minutes to eat until comfortably full. The buffet meal consists of 300ml orange juice, 600ml water, 375ml iced coffee, 4 slices white bread, 4 slices brown bread, 100g deli leg ham, 100g virginian chicken, 4 slices cheese, 100g tomato, 100g cucumber, 100g lettuce, 2 portions mayonnaise, 2 portions margarine, 1 medium apple, 1 medium banana, 200g chocolate custard, 150g fruit salad, 200g strawberry yoghurt, and a 14g milky way chocolate bar. Each volunteer will receive one of each infusion solutions on each of the 4 study days. Each study visit will be separated by no less than 3 days. Each study visit will last approximately 3‐6 hours. CONDITION: Obesity PRIMARY OUTCOME: Antropyloroduodenal Motility (antropyloroduodenal pressures, number of antral, duodenal and isolated pyloric pressure waves, and basal pyloric pressure) assessed by Manometry. Appetite sensations using a Visual Analogue Scale (VAS) (satiety, hunger, fullness, thirst, desire to eat and amount of food desired to eat) Gut Hormone release: cholecyctokinin (CCK), glucagon‐like peptide‐1 (GLP‐1), peptide YY (PYY), and Ghrelin. ; ; Gut hormone release will be assessed by Enzyme‐Linked Immunosorbent Assay (ELIZA) from the blood samples taken. SECONDARY OUTCOME: Macronutrient and total energy intake at the buffet meal will be analysed using the FoodWorks software program. INCLUSION CRITERIA: non‐obese with a Body Mass Index (BMI) of 18‐25kg/m2 and obese with a BMI of 27‐35kg/m2 Weight stable (<5% fluctuation in body weight in previous 3 months)