Effects of acute and longer-term energy restriction in lean and obese subjects on gut motility, hormones, appetite and energy intake in response to small intestinal nutrients and on oral fat perception

Obese subjects will undergo a 12-week period of dietary restriction which will entail a 30% reduction of total energy intake, using a macronutrient-balanced (15% protein, 55% carbohydrate, 30% fat) diet. A standard 6000, 7000kJ and 8000kJ dietary intake using Lite and Easy menu structure will be utilised. Lean individuals will only be studied during a 4-day period of dietary restriction. During this time subjects will be given a complete meal plan to follow on a day-to-day basis and a meal check list to ensure they comply with the diet. The meal plan will contain a variety of foods for the subject to consume to ensure a varied diet. Compliance with the diet will be checked regularly throughout the study by a dietician, and subjects will be provided with all study food, including all meals and snacks, to facilitate adherence to the diet. Obese subjects will attend the laboratory on 4 days and lean subjects will attend on 2 days, to evaluate the effects of the dietary manipulations on GI motility, hormone release, appetite and energy intake in response to intraduodenl infusion of fat (Intralipid) at a rate of 2.86 kcal/min for 120 min. At the end of each study day, oral fatty acid taste thresholds will also be determined in each individual.