Caloric-restrictive diets have been prescribed for obesity since the times of Hippocrates, and still today is the most prescribed therapeutic modality by front line healthcare providers. But yet dieting has 97% failure rate measured over 5-7 year follow periods
A review by Traci Mann and colleagues found in a 25 retrospective review of diets, that between 33-67% of dieters gain back more weight than they had lost
Such a failure in pharmaceutical drugs would not pass FDA review, and therefore not be approved as a medical therapy.