A hypocaloric diet, whatever the proposed type, is an inadapted treatment to chronic disease, like obesity. All diets are inefficient on the long term. The weight loss is generally small, about 1-2 kg a year. The results are the same, independently of the type of diet, and the patient's compliance is clearly the main key to succeed. About 80% of patients regain weight the first month following the diet, and only 1% can keep the obtained weight a year later. Nearly half of the patients involved in a diet program give up before the end. Finally, because of risks of macro and micro nutriments deficiency, certain diets are to be avoided and hypocaloric diet shouldn't be proposed.