Effects of Obesity Treatments on Food Preferences and Metabolism

Overview

Obesity and Type 2 Diabetes Mellitus are major health problems which are becoming a burden both for patients and health systems alike. The surgical and medical treatments available for these conditions have improved significantly in the last two decades. The investigators do not however know how these treatments compare to each other and how they act in the body to cause weight loss and diabetes improvements. The studies of this experiment are complementary to each other. They aim to answer related questions and will allow us to study how these treatments work and eventually develop safer and more effective therapies for obesity and diabetes.

The objective of this study is to investigate the effects of obesity surgical procedures and incretin therapies on food preferences, satiety, gut hormones, bile acids and hepatic glucose output in overweight and obese patients. As part of routine care these patients will be seen by a dietician/diabetes specialist nurse (DSN) before and after intervention. Patients will be asked to prospectively complete food diaries on three consecutive days which are representative of their usual dietary intake. The first food diary will be completed three months to two weeks pre intervention. Another four food diaries will be completed post intervention: at one, three months, 6 months and one year. Total energy intake and macronutrient composition comparisons pre and post intervention will form the basis of our analysis. 20 patients in each group will undergo more detailed measurements of food intake, hunger, satiety, gut hormones and bile acids. The research protocol will be the similar to that previously published by the Department of Metabolic Medicine, Imperial College, London. Participants will be fasted for 12 hours overnight and will attend for the study on 5 occasions. On each occasion venous blood samples will be taken and visual analogue scores will be measured over a 3 hour period using previously published methodology Samples or sample containers will be anonymised before collection but will be traceable back to the individual patients. Urine will be collected once. A qualified medical doctor will insert a venepuncture cannula into the arm of the patient and 5ml blood will be withdrawn at baseline, 15, 30, 60, 90, 120, 150 and 180 minutes following ingestion of a standard 400kcal meal as below. Ten patients in each group (different from those taking part in the meal studies) will undergo measurements of hepatic glucose output/insulin resistance through euglycaemic hyperinsulinaemic clamps (Metabolic Study). To ensure that acute caloric restriction does not affect insulin sensitivity, patients will be on a low calorie liquid diet for 4-14 days and 3-7 days after intervention to ensure that their weight is stable throughout the study. This diet is nutritious and contains all appropriate macronutrients. Such diets are frequently used as part of pre-obesity interventions to reduce weight and risk. Patients will provide the investigators with a detailed food diary of their food consumption for this period.