[Principles of dietary treatment of obesity]

One of the first steps in a clinical approach to any obese subject should be focused on the reduction and/or normalization of any potential or existing metabolic abnormality. Overeating and/or unbalanced food intake remains the major element in the origin and maintenance of obesity. The reduction of energy intake is the basis of successful weight loss. In obese subjects there are huge amounts of energy stored, mainly in the adipose tissue, which are mobilized according to the size and duration of an energy deficit. Considerable studies have been devoted to finding the optimal dietary approach that would promote rapid weight loss while maximizing the depletion of adipose tissue and conserving body protein. During fasting adipose tissue lipolysis rate increases and liberated unesterified fatty acids are oxidized in muscle and liver. The liver produces ketones which are oxidized in muscle and brain. The energy need of the brain is not sufficiently covered by ketone oxidation, therefore additional glucose must be provided. The liver produces glucose by gluconeogenesis using amino acids from muscle protein. Because of limited protein sources, protein must be given during energy restricted diet. Besides protein also vitamins, minerals, trace elements, fiber, and linoleic acid must be substituted during fasting and during treatment with very low calorie diets. Meal replacements are helpful to fulfil all the requirements. There is consensus that the first step in dietary treatment is an energy restricted diet with a calorie deficit of at least 600 Kcal/day, but more than 800 Kcal/day must be provided, with all essential nutrients. Observing the regulations, weight reduction with appropriate diet plans improves metabolic disturbances.