Effects of Weight Loss on Nutritional Mediated Hormone Secretion

Investigative trial with aim of 1. the description of the hormonal and metabolic response to meals containing different compositions of macronutrients 2. the metabolic response to these test meals in dependance of the hepatic and muscular insulin sensitivity and abdominal adipose tissue and 3. effects of a weight loss on the hormonal response to these test meals containing different compositions of macronutrients Primary endpoint: Glucagon-like-peptide 1 (GLP-1), Glucose dependent insulinotropic peptide (GIP) and Ghrelin response to a nutritive stimulation characterized by different nutritional composition Secondary endpoints: * differences of substrate utilization depending on the nutritive composition * effects of different hepatic and muscular insulin sensitivity as well as impact of visceral fat mass on the hormonal and metabolic response * effect of weight loss on the hormonal and metabolic response to different test meals Study procedure: After primary characterization 50 probands (male and female) will receive 3 different test meals within a randomised (meal order) controlled trial. The three different test meals differ in nutritional composition. During consumption of the test meal a characterization of the endogenous hormonal response and appetite behaviour is performed. A nutritional counselling is performed according to the guidelines of the German Nutrition Society (DGE) to ensure a stable nutritive behaviour in the three days before the test meal administration. After analysis of the hormonal response to these 3 different testmeals follows a weight reduction period over 3 months. Afterwards reevaluation of the probands (again administration of 3 different test meals over a period of 3 weeks) will be performed. Principal aim of the study: Gain of information leading to the understanding of the hormonal regulation of food intake. The individual variability shall be determined with the aim of an identification of patient groups which show vario