Long Term Effects of Weight Loss on Post-prandial Gut Hormone Responses and Meal Induced Thermogenesis

This is a protocol for the study of post-prandial gut peptide response and meal-induced thermogenesis in a group of 15 conservatively managed (through diet and exercise) morbidly obese individuals. During two separate visits in the study site, anthropometric and bioelectric impendence data will be collected, resting metabolic rate will be measured, and the patients will undergo a panel of cardiovascular examinations (heart rate variability, baroreflex sensitivity, heart ultrasound). On a separate occasion, they will consume a standardized test mixed meal and complete visual analog scales for the subjective assessment of hunger and fullness every 30 minutes for 3 hours. At the same time points, blood samples will be collected for the consequent measurement of glucose, insulin, lipids, and gastrointestinal hormones. Additionally, immediately before and at 60', 120', 180' after the start of the consumption of the test meal, the resting metabolic rate of each participant will be assessed through indirect calorimetry, to quantify meal-induced thermogenesis. The observed induction of satiety and suppression of hunger, post prandial gut-peptide mobilization and change in metabolic rate will be compared to those of participants of trial no NCT03851874 (Morbidly obese patients that have undergone either Roux en Y gastric bypass or sleeve gastrectomy and participated in trial NCT03851874). Participants in the aforementioned cohort have been already followed-up during the first postoperative year and will attend the study site for another follow-up visit approximately 10 years postoperatively, whereby the same diagnostic evaluation described above will take place. Data analysis will take place within the bariatric cohort (longitudinal analysis of the effects of surgery and surgery types on anthropometric parameters, fasting and postprandial glycemia and lipemia, fasting NMR-Metabolomic/Lipidomic profiles, Indices of insulin resistance, echocardiography, energy expenditure) as well as between the two groups in a cross-sectional manner.