[Nutrition physiological aspects in the treatment of obesity]

Obesity is one of the most common prosperity diseases. As a consequence of this disease there is a decrease in the expectation of life. Obesity is bascially caused by overeating. The low-caloric reducing diets are differentiated into a low-fat and high-carbohydrate form, and into a carbohydrate-free and high-fat diet. The metabolic advantages and the disadvantages of these two forms of low-caloric diets are discussed with respect to starvation metabolism. It is assumed that without ketoacidosis, at least 100-140 g glucose per day are required to meet the energetic demands of the central nervous system. Since the conversion rate of protein to glucose is about 2:1, during a carbohydrate-free diet about 200-260 g of protein per day would be necessary to meet the glucose requirements of the organism. As such a high-protein supply with food is almost impossible, ketogenesis in the liver must take place as a sort of "glucose-sparing mechanism". Only under these conditions, the otherwise extreme nitrogen catabolism can be avoided during an almost carbohydrate-free diet. However, using a fat-free (600 kcal) diet it is possible to furnish the glucose requirements of the central nervous system by the food supply. Therefore, a compensatory ketoacidosis is not required. Additionally, the fat-free diet does not contain cholesterol. In this way, the hypercholesterinemia which is a common feature in obesity is favourably influenced by the absence of foods of animal origin. Therefore, within a short period a marked decrease in serum cholesterol concentration results by the high-carbohydrate diet. The same is true for the concentration of free fatty acids and serum triglycerides. It is concluded that the high-carbohydrate low-caloric diet is suited best for reduction of body weight.