Anorexia nervosa is characterized by a relentless pursuit of thinness, a distorted body image, an extreme fear of obesity, and restriction of food consumption, leading to a significantly low body weight.
Hereditary and social factors play a role in the development of anorexia nervosa. The desire to be thin pervades Western society, and obesity is considered unattractive, unhealthy, and undesirable. Even before adolescence, children are aware of these attitudes, and more than half of preadolescent girls diet or take other measures to control their weight. Yet only a small percentage of these girls develop anorexia nervosa. Other factors, such as psychologic susceptibility and genetic make-up, probably predispose certain people to develop anorexia nervosa. In areas with a genuine food shortage, anorexia nervosa is rare.
The disorder usually begins during adolescence or young adulthood and rarely begins before puberty or after age 40. Anorexia nervosa affects primarily people in middle and upper socioeconomic classes. In Western society, the number of people who have this disorder seems to be increasing. In a given year, about 1 in 200 young females have anorexia nervosa. The disorder is much less common among males. However, mild cases may not be identified.
There are two types:
Anorexia nervosa may be mild and transient or severe and persistent.
The first indications of the impending disorder may be a subtle increased concern with diet and body weight. Such concerns seem out of place because most people who have anorexia nervosa are not overweight. Preoccupation and anxiety about weight intensify as people become thinner. Even when emaciated, people claim to feel fat, deny that anything is wrong, do not complain about weight loss, and usually resist treatment. They continue to try to lose weight even when friends and family members reassure them that they are thin or warn them that they are getting too thin. People with anorexia nervosa view any weight gain as an unacceptable failure of self-control.
Anorexia literally means lack of appetite, but people who have anorexia nervosa are actually hungry and preoccupied with food. But rather than eat, they study diets and count calories. They may hoard, conceal, or throw away food. They may collect recipes and prepare elaborate meals for others.
About 30 to 50% of people who have anorexia nervosa binge and/or purge by vomiting or taking laxatives. The others simply restrict the amount of food they eat. They also frequently lie about how much they have eaten and conceal their vomiting and their peculiar dietary habits. Some people also take diuretics (drugs that cause the kidneys to excrete more water) to reduce perceived bloating and to try to lose weight.
Many women with anorexia nervosa stop having menstrual periods, sometimes before losing much weight. Women and men may lose interest in sex.
Typically, people with anorexia nervosa have a low heart rate, low blood pressure, a low body temperature, and may develop fine soft hair on their body, or excess body and facial hair. Tissues swell because fluid accumulates (called edema). People commonly report bloating, abdominal distress, and constipation.
Self-induced vomiting can erode tooth enamel, enlarge the salivary glands in the cheeks (parotid glands), and cause the esophagus to become inflamed. Depression is common.
Even when people become very thin, they tend to remain active, often exercising excessively to control their weight. Until they become emaciated, they have few symptoms of nutritional deficiencies.
Hormonal changes resulting from anorexia nervosa include markedly reduced levels of estrogen (in women), testosterone (in men), and thyroid hormone and increased levels of cortisol.
If people become severely malnourished, every major organ system in the body is likely to be affected. Bone density may decrease, increasing the risk of osteoporosis.
Rapid or severe weight loss can cause life-threatening problems. Problems with the heart and with fluids and electrolytes (such as sodium, potassium, and chloride) are the most dangerous:
Vomiting and taking laxatives and diuretics can worsen the situation. Sudden death, probably due to abnormal heart rhythms, may occur.
Because people do not think they have a problem, they resist evaluation and treatment. Usually, they are brought to the doctor's office by family members, or they come because of another disorder.
Doctors measure height and weight and use the results to calculate the body mass index (BMI—see Overview of Nutrition). Doctors also ask people how they feel about their body and weight and whether they have other symptoms. Doctors may use questionnaires developed to detect eating disorders. If people have the following, anorexia is likely:
Doctors also do a physical examination and blood and urine tests to check for effects of weight loss and undernutrition. A bone density test may be done to check for loss of bone density (see Dual-Energy X-Ray Absorptiometry (DXA)). Electrocardiography (ECG) may be done to check for abnormal heart rhythms (see Electrocardiography).
Without treatment, nearly 10% of people with severe anorexia die. When symptoms are mild and unrecognized, people rarely die.
With treatment, about one half of people regain most or all of the weight they lost, and hormonal and other physical problems due to the disorder resolve. About one fourth improve some, gaining some weight back, but they may periodically return to their former eating habits (relapse). The remaining one fourth have frequent relapses and continue to have physical and mental problems due to the disorder.
Children and adolescents treated for anorexia nervosa have better outcomes than adults.
When weight loss has been rapid or severe (for example, to more than 25% below the ideal body weight), restoring body weight quickly is crucial. People with anorexia nervosa may need to be hospitalized to ensure that they consume enough calories and nutrients. Although eating food is the best treatment, people rarely need to be fed through a tube inserted through their nose and down their throat into their stomach (nasogastric tube).
Doctors also check for problems due to anorexia nervosa, and any problems are treated. For example, if bone density has been lost, people are given calcium and vitamin D supplements. During hospitalization, psychiatric and nutritional counseling are provided. Hospitalization also helps by taking people out of their normal circumstances and disrupting their dysfunctional eating habits and behaviors. Thus, it may reverse a downhill course. However, most people are treated as outpatients.
Psychologic therapy that emphasizes establishing normal eating habits and attaining a normal weight is often used. Such therapy includes individual and family psychologic therapy, such as cognitive-behavioral therapy. Typically, therapy is continued for 1 full year after people have regained the lost weight. It may take up to 2 years.
Family therapy is useful for adolescents. It can improve interactions among family members and teach parents to help the affected adolescent regain the lost weight. Therapy is more effective for adolescents who have had the disorder for less than 6 months.
Therapy is particularly important because many people with anorexia nervosa are somewhat reluctant to be treated or to regain weight.
Treatment also involves seeing a doctor regularly for check-ups. It often involves a team of health care practitioners, including a nutritionist, who may provide specific meal plans or information about the calories needed to restore weight to a normal level.
There are no specific drugs to treat anorexia nervosa. However, newer antipsychotic drugs, such as olanzapine, may help people gain weight and relieve their anxiety.
Last full review/revision December 2014 by Evelyn Attia, MD; B. Timothy Walsh, MD