Eating Disorders

While obesity and eating disorders both involve eating behaviors, they are very different things. Obesity is considered a metabolic disorder characterized by excess fat on the body that contributes to ill health. It is associated with eating too many calories from food and not expending enough calories in physical activity. Eating disorders are mental disorders characterized by distortions in body image, control issues and other psychological concerns.

Both obesity and eating disorders are health conditions that are diagnosed based on specific medical criteria.

Characteristics of Obesity and Eating Disorders
Obesity is diagnosed by having a Body Mass Index (BMI) of 30 or higher. [For more information on diagnosing overweight and obesity, refer to The Body Mass Index.] The diagnosis of eating disorders, however, is more complex because there are two distinct types. The diagnosis of anorexia nervosa includes having a significantly low body weight in the context of age, sex, developmental trajectory and physical health. In addition, this disorder is distinguished by a disturbance in perception of body weight or shape and persistent lack of recognition of the seriousness of the current low body weight.¹

Bulimia nervosa differs from anorexia nervosa in that there is no weight definition. Rather, a diagnosis is made from a regular pattern (e.g., at least once per week for at least three months) of binge eating followed by purging. The purging can consist of self-induced vomiting or the improper use of laxatives, diuretics, enemas, fasting or excessive exercise.¹

Binge eating disorder has been proposed for inclusion as a free-standing diagnosis.¹ It is defined as eating, in a discrete period of time (e.g., within any 2-hour period), an amount of food that is definitely larger than most people would eat in a similar period of time under similar circumstances, and as a sense of lack of control over eating during the episode (for example, a feeling that one cannot stop eating or control what or how much one is eating). Another eating disorder, night eating syndrome, does not have a clear set of diagnostic standards and as such is not a DSM-5 diagnosis.²

Prevalence of Eating Disorders
Only a qualified health professional can make the diagnosis of an eating disorder. Unfortunately, there are many people who fear having an eating disorder when they do not (e.g., having an occasional episode of overeating does not constitute a binge nor does it make one a binge eater). In fact, the estimated frequency of eating disorders is small. Approximately 0.6 percent of people have anorexia nervosa and 1 percent have bulimia nervosa in the United States, ² with comparable numbers seen in the United Kingdom and Australia.

While reducing excess fat from obesity can be accomplished with a comprehensive weight-loss program, the treatment of medically diagnosed eating disorders requires more intensive treatment by qualified health care professionals.

¹ American Psychiatric Association. DSM-5 Development.

²Hudson JI, Hiripi E, Pope HG, Kessler RC. The prevalence and correlates of eating disorders in the National Comorbidity Survey Replication. Biol Psychiatry. 2007 Feb; 61(3): 348-58.