Changes in Gut Hormones, Body Composition and Energy Expenditure After Roux-en-Y

Each subject will have their resting metabolic rate (RMR) measured. The RMR is assessed by indirect calorimetry measured with the metabolic cart. Oxygen consumption is converted into kilocalories. Subjects will be advised to avoid strenuous exercise for at least 48 hours prior to participation in the study and to sleep at least 6-8 hours the night before. Smoking and consuming caffeine will be prohibited 12 hours before the study begins.

During a separate appointment on the same day, or within 7 business days if same day is not possible, a body compositions analysis, including fat mass and fat free mass, will be assessed by dual-energy x-ray absorptiometry (DEXA), using a Hologic system.

Subjects will be asked to complete a 100-mm Visual Analog scale (VAS) to assess their appetite. The VAS will be completed prior to the meal stimulation test and at 30-minutes, 1-hour, 90 minutes and 2-hours after the meal. The VAS will contain questions assessing food intake, appetite, and hunger.

Subjects will consume a mixed-nutrient liquid meal 240-ml in 20 minutes. Prior to the meal stimulation test, a baseline 10-ml blood sample will be collected. The, during the meal stimulation test, 10-ml venous blood sample will be collected at 30 minute intervals up to two hours, for a total of 5 samples including the baseline sample. The blood samples will be used to measure fasting blood glucose, adipokines, myokines, gut hormones, amino acids, bile acids, vitamin B and vitamin D analysis with the appropriate assay method.