Comparative effects of intraduodenal macronutrients, carbohydrate, lipid and protein, and combinations of lipid and protein, on gut motility, hormones, appetite and energy intake in lean subjects

INTERVENTION: Study 1 and Study 2 will be conducted seperately and consist of different volunteers. Subjects within each study will undergo 5 treatments, in double‐blind, randomised, cross over fashion. Gastrointestinal (GI) motility, hormone release, appetite and energy intake will be evaluated. The nutrient infusions will be administered for 120 min at a rate of 3 kcal/min, corresponding to the average rate of postprandial gastric emptying treatments. Treatments within each study will be separated by 7‐10 days. Study 1 will evalutate: i) lipid ii) carbohydrate iii) protein iv) macronutrient combination of lipid:carbohydrate:protein (30:50:20) v) saline control Study 2 will evaluate: i) lipid ii) protein iii) protein:lipid (2:1) iv) protein:lipid (1:2) v) saline control CONDITION: To compare in healthy, lean individuals the effects of combinations of lipid and protein, on antropyloroduodenal motility, gut hormone release, appetite and energy intake. To compare in healthy, lean individuals the effects of the three macronutrients, carbohydrate, protein and fat, on antropyloroduodenal motility, gut hormone release, appetite and energy intake. PRIMARY OUTCOME: Antropyloroduodenal motility ‐ During the 120 minute infusion antropyloduodenal motility was assessed via changes in the pressures within specific portion of the gastrointestinal tract (antrum, pylorus and duodenum) which was captured by sensors on the catheter, and connected to a computer‐based system, running commercially available hardware (Flexisoft) SECONDARY OUTCOME: Appetite and hunger ‐ Using visual analogue scale questionnaires Energy intake ‐ At t = 120 min the infusion will be discontinued, and the subject extubated and offered a cold buffet‐style meal (t = 120 ‐ 150 min). The meal will be weighted before and after consumption to for the assessment of energy intake using Foodwork Hormone release ‐ Cholecystokinin (CCK) and Peptide YY (PYY). Blood samples were drawn from subjects every 15 minutes until t=90, and then once more at t=120. Radioimmuno assays were used to determine the concentration of these hormones in plasma. INCLUSION CRITERIA: Subjects will all be healthy males between age 18 ‐55 years, with a body mass index (BMI) of 18 ‐ 25 kg/m2. Subjects will be required to be unrestrained eaters, consume less than 20g of alcohol per week, be non‐smokers, free of gastrointestinal or chronic disease and not currently taking medication.