An eating disorder is marked by extremes. It is present when a person experiences severe disturbances in eating behavior, such as extreme reduction of food intake or extreme overeating, or feelings of extreme distress or concern about body weight or shape.

A person with an eating disorder may have started out just eating smaller or larger amounts of food than usual, but at some point, the urge to eat less or more spirals out of control. Eating disorders are very complex, and despite scientific research to understand them, the biological, behavioral and social underpinnings of these illnesses remain elusive.

The two main types of eating disorders are anorexia nervosa and bulimia nervosa. A third category is "eating disorders not otherwise specified (EDNOS)," which includes several variations of eating disorders. Most of these disorders are similar to anorexia or bulimia but with slightly different characteristics. Binge-eating disorder, which has received increasing research and media attention in recent years, is one type of EDNOS.

Eating disorders frequently appear during adolescence or young adulthood, but some reports indicate that they can develop during childhood or later in adulthood. Women and girls are much more likely than males to develop an eating disorder. Men and boys account for an estimated 5 to 15 percent of patients with anorexia or bulimia and an estimated 35 percent of those with binge-eating disorder. Eating disorders are real, treatable medical illnesses with complex underlying psychological and biological causes. They frequently co-exist with other psychiatric disorders such as depression, substance abuse, or anxiety disorders. People with eating disorders also can suffer from numerous other physical health complications, such as heart conditions or kidney failure, which can lead to death.

Types of eating disorders:

Anorexia Nervosa

Bulimia Nervosa

Binge-Eating Disorder

Treatment

Researchers are unsure of the underlying causes and nature of eating disorders. Unlike a neurological disorder, which generally can be pinpointed to a specific lesion on the brain, an eating disorder likely involves abnormal activity distributed across brain systems. With increased recognition that mental disorders are brain disorders, more researchers are using tools from both modern neuroscience and modern psychology to better understand eating disorders.

One approach involves the study of the human genes. With the publication of the human genome sequence in 2003, mental health researchers are studying the various combinations of genes to determine if any DNA variations are associated with the risk of developing a mental disorder. Neuroimaging, such as the use of magnetic resonance imaging (MRI), may also lead to a better understanding of eating disorders.

Neuroimaging already is used to identify abnormal brain activity in patients with schizophrenia, obsessive-compulsive disorder and depression. It may also help researchers better understand how people with eating disorders process information, regardless of whether they have recovered or are still in the throes of their illness.

Conducting behavioral or psychological research on eating disorders is even more complex and challenging. As a result, few studies of treatments for eating disorders have been conducted in the past. New studies currently underway, however, are aiming to remedy the lack of information available about treatment.

Researchers also are working to define the basic processes of the disorders, which should help identify better treatments. For example, is anorexia the result of skewed body image, self esteem problems, obsessive thoughts, compulsive behavior, or a combination of these? Can it be predicted or identified as a risk factor before drastic weight loss occurs, and therefore avoided?

These and other questions may be answered in the future as scientists and doctors think of eating disorders as medical illnesses with certain biological causes. Researchers are studying behavioral questions, along with genetic and brain systems information, to understand risk factors, identify biological markers and develop medications that can target specific pathways that control eating behavior. Finally, neuroimaging and genetic studies may also provide clues for how each person may respond to specific treatments.

Source: National Institute of Mental Health