Obesity is a very common disease which is increasing in prevalence and severity. Public health measures may be used for prevention but are ineffective for treatment. Body weight is vigorously defended via several physiological mechanisms, and weight regain occurs in 90% of those who lost weight, regardless of the tempo of weight loss. The most effective medical weight loss strategy involves a period of rapid weight loss achieved with a very low calorie died (VLCD), with the assistance of an appetite suppressant such as topiramate, a GLP-1 agonist or phentermine.