The prognosis for obesity is poor, untreated, it tends to progress. Attempts to lose weight may cause complications, symptoms of anxiety and depression may appear in as many as half of patients undergoing medical treatment. Treatment is still only modestly effective but is improving. The aim of therapy is to establish a caloric deficit by reducing the number of food calories below the number of calories expended as energy. Methods to achieve this deficit vary widely and may seem confusing.
Severe obesity is relatively uncommon.
The basis of treatment is surgery , which can produce large weight losses that are often well maintained. Such surgery is not without risk, and should be used only in severely obese persons who have repeatedly failed at conservative treatments. Most operations radically reduce stomach volume, either by vertical-banded gastroplasty or by gastric bypass. Weight loss after surgery is at first quite rapid, slowing gradually over 2 yr. The goal of diet therapy is to establish the largest caloric deficit that can be safely and comfortably tolerated.