The dietary treatment for weight loss in overweight and obesity has been approached in many different dietary models. Nevertheless, besides the size of weight loss, the main outcomes should be mostly the improvement of body composition (loss of body fat and preservation of lean body mass), long-term maintenance, nutritional quality of the diet, lower risk for chronic diseases (better metabolic parameters), improvement in quality of life and psychological well-being. The most popular diets have been analyzed: high protein diets (HPD), low-carbohydrate diets (LChoD) and low glycemic index or load diets (LGID), low-fat diets (LFD), low calorie diet (LCD) and very-low-calorie diet (VLCD), and ketogenic diets (KD). In the end, the criteria for the development of a balanced dietary treatment in obese patient are discussed as a result of a critical analysis of the different dietary patterns described. Several evidences lead to the conclusion that the Mediterranean dietary pattern better respects the clinical guidelines for overweight and obesity treatment. In order to achieve a good compliance and the subsequently long-term results, the multidisciplinary approach, based on nutritional counseling, physical activity, together with the cognitive-behavioral therapy, is the only reasonable therapeutic option.