It must be readily understood that the only possibility of fighting obesity is by bringing about a reversal in the energy balance so that inputs are smaller than outputs. At least theoretically, then, obesity's special quality is that it does not present any therapeutic problem. Restriction in food intake is currently the treatment of choice; to be effective, food intake must be cut so that the energy provided is below the obese person's daily consumption, on average below 1200 calories per day, while at the same time holding a comparatively high intake of indispensable elements (proteins, vitamins, certain minerals and oligo-elements). The physician has a choice of various possibilities represented by fasting, a variety of free or controlled diets, protein diets or diets with low carbohydrate content and with a variable fat content; dissociated, zig-zag, one food diets etc. Substantially all these tend to limit the total quantity of glycides and boost the feeling of satiety by increasing the total volume of good while keeping total calories unvaried. It is clear that each of them has specific indications and clear-cut contraindications. The aim is to produce a calory shortfall, not cause denutrition. The diet must therefore be suited to the individual directed during subsequent stages of weight loss in relation to the patient's specific requirements (number of meals, etc.).