Psychiatric Comorbidity
As noted, as many as 50% of obese individuals engage in recurrent binge eating. Approximately one-fourth of obese binge eaters meet the diagnostic criteria for major depression compared with fewer than 5% of nonbingers. Obese binge eaters are twice as likely as nonbingers to have anxiety disorders, four times as likely to suffer from social phobia, and three times as likely to have drug or alcohol problems than nonbingers.

Medical Complications
It is estimated that more than 90% of cases of Type II diabetes, 70% of gallstones, 60-70% of coronary artery disease, 11% of breast cancers, and 10% of colon cancers are attributable to obesity.

Excess weight may cause low back pain, aggravation of osteoarthritis (particularly of the knees and ankles), and huge calluses on the feet and heels. Obesity may be associated with amenorrhea and other menstrual disturbances. The lower ratio of body surface area to body mass leads to impaired heat loss and increased sweating. Intertrigo in tissue folds, itching, and skin disorders are common. There is often mild to moderate swelling of hands and feet.

In massively obese persons, pressure of fatty tis-sue on the thorax combined with pressure of intra-abdominal fat on the diaphragm may reduce respiratory capacity and produce dyspnea on exertion. This condition may progress to the so-called pickwickian syndrome, characterized by hypoventilation with hypercapnia, hypoxia, and somnolence.

Natural History
Obesity can begin in childhood, adolescence, or adulthood. Amounts of body fat also increase with age even when weight remains constant. Obesity is usually a chronic and progressive condition. It is estimated that 300,000 deaths per year are caused by weight-related conditions, making obesity second only to cigarette smoking as the leading cause of preventable death in the United States.