Possible causes of the disorders

Many people view eating disorders as self-destructive acts however most individuals who develop eating disorders do not usually perceive their behaviors as self-harmful. Actually, most feel that they began the behaviors to try to fix other problems. The most common reason therapists hear from people about why they began self-starvation, bingeing or purging is that at some point they felt terribly out of control -- whether because of something they were feeling inside themselves or something that was happening to them from their outside environment.
Below are some of the most common causes of eating disorders:
Major life transitions. Many patients with eating disorders have difficulty with change. Anorexics, in particular, typically prefer that things are predictable, orderly and familiar. Consequently, transitions such as the onset of puberty, entering high school or college, or major illness or death of someone close to them can overwhelm these individuals and cause them to feel a loss of control.
Family patterns and problems. The National Eating Disorders Association cites troubled family relationships as a possible contributing factor to eating disorders. Some, but not all individuals with eating disorders, come from disordered families.
Social problems. Most people who develop eating disorders report having painfully low self-esteem before the onset of their eating problems. Many patients describe going through a painful experience such as being teased about their appearance, being shunned, or going through a difficult break-up of a romantic relationship.
Failure at school, work or competitive events. Eating disorder patients can be perfectionists with very high achievement expectations. If their self-esteem is disproportionately tied to success, then any failure can produce devastating feelings of shame, guilt or self-worthlessness.
A traumatic event. Evidence continues to accumulate that between one- third and two-thirds of patients who go to treatment centers for eating disorders have histories of sexual or physical abuse.
Major illness or injury can also result in an individual feeling extremely vulnerable or out of control. Anorexia and bulimia can be attempts to control or distract themselves from such trauma.
Other psychiatric illnesses. Researchers have found that some people develop eating disorders in response to other psychiatric symptoms that occurred first.
Between one-third and one-half of patients report having struggled with significant depression or anxiety before their eating disorder began.
Excessive exercise, and/or binge-purge behavior to contain or manage the depression and anxiety.

Johnson, Craig. "The Many Causes of Eating Disorders". Healthy Place. March 11, 2010 .