More than half a million women between 12 and 25 in the U.S. have an eating disorder, according to the American Psychiatric Association Anorexia and bulimia are the best known_and the most dangerous, notes the APA's Diagnostic and Statistical Manual of Mental Disorders.

But researchers are now beginning to diagnose a host of other eating-related ailments that affect people of all ages and both sexes. Here's a guide:

Anorexia Nervosa

Diagnosis: Refusal to maintain a minimally normal body weight.

Most likely candidates: An estimated one out of every 100 girls and young women; typical sufferer is young (17 to 25), white, upper-middle-class, well-educated.

Characteristics: Weight loss to 85% below a minimally normal weight of person's age and height; intense fear of gaining weight or becoming fat; loss of menstrual cycle.

Danger signs: Drastic weight loss; preoccupation with being thin; distorted body image; depression.

Cause: Anorexics tend to be perfectionists and high achievers but lack self-esteem. Other theories: a brain chemical imbalance, perhaps a genetic influence.

When happens: Often begins in adolescence as an "innocent diet" and can disappear on its own or grow steadily worse. One-third of cases last five to 10 years.

Treatment: Treatment can include psychotherapy, behavior modification, nutritional counseling and self-help groups. Family support is essential.

Binge Eating Disorder

Diagnosis: Recurrent episodes of binge eating, but not followed by purging or use of laxatives. The disorder has not yet been officially recognized by the APA.

Most likely candidates: Mostly overweight women, but approximately 35% of sufferers are men.

Characteristics: Frequent, uncontrolled eating binges at least twice weekly, often driven by emotional upset, followed by feelings of distress and guilt; persistent or recurrent obesity.

Danger signs: Eating larger-than-normal amounts of food in a two-hour span, such as a whole pizza or gallon of ice cream; recurrent depression.

Cause: Unclear, but studies show that bingers often suffer from depression.

When happens: Usually starts after adolescence; often goes undiagnosed in cases of obesity. 

Treatment: Antidepressant and therapy followed by weight-control strategies.

Bulimia Nervosa

Diagnosis: Recurrent episodes of binge eating and purging. Bulimia is more common than anorexia (it has been officially diagnosed as a separate problem only since the 1980s).

Most likely candidates: Up to 35% of college women use bingeing and purging to control their weight. About 50% of anorexics will develop bulimia.

Characteristics: Recurrent episodes of binge eating, averaging about 5,000 calories per episode, followed by induced vomiting or large doses of laxatives; feeling out of control during binges.

Danger signs: Bulimia is difficult to diagnose because many individuals maintain a normal weight. Signs include mood swings and depression, puffy skin, thick white saliva, trips to the bathroom after eating.

Cause: Unclear, but like anorexia, it may result from social pressure to be thin coupled with poor self-image. Studies have shown that bulimics are at higher risk for depression, alcohol and drug abuse.

When happens: Typically starts later than anorexia; most bulimics seek treatment in their mid-20s and 30s. Continual purging can damage stomach, esophagus and liver, and erode tooth enamel.

Treatment: Early intervention and long-term treatment are necessary. Therapy is similar to that for anorexia, but antidepressants like Prozac may also be prescribed.

Exercise Resistance

Diagnosis: An entrenched inactivity pattern resistant to exercise. This is a new diagnosis that is still being researched.

Most likely candidates: Tends to affect compulsive eaters and overweight individuals who feel exercise is done solely to lose weight.

Characteristics: Resistance to suggestions to become physically active; evidence of moderate to severe anxiety during physical activity.

Danger signs: Can become angry, resentful or anxious at suggestions to become more physically active.

Cause: Occurs at any age; usually seen in those moderate to severe overeating histories.

Treatment: Therapy that focuses on underlying psychological issues rather than on weight and fitness.

Night Eating Syndrome

Diagnosis: Fifty percent or more of daily food intake occurs at night. Researchers first identified the disorder in 1955, but it has not been officially recognized by the APA.

Most likely candidates: A recent study suggests that 10% of obese people have the disorder.

Characteristics: Night eaters wake up hungry in the middle of the night and prepare a series of small meals, believing food will put them back to sleep.

Danger signs: No appetite for breakfast, difficult falling or staying asleep; tendency toward irregular eating habits and lack of balanced meals; solitary eating.

Cause: Disruption of the circadian rhythm. People with long, stressful workdays and/or who live alone tend to have night eating habits and may be at greater risk.

When happens: Often occurs when a person is experiencing anxiety, heavy fatigue or long bouts of stress.

Treatment: Retraining eating habits; consuming a good lunch, midday carbo snack, early dinner. Engaging in evening activities (like writing letters) to avoid eating.

Restricted Eating

Diagnosis: Intentionally going hungry by constantly being on strict diets. Can lead to bingeing. Not an official disorder, but a long-term dieting pattern.

Most likely candidates: Up to 50% of the female population, typically chronic dieters.

Characteristics: Habitual adoption of strict diet; rigid feeding patterns (calorie counting, precise portion control, avoiding food groups); ignorance of body's hunger signals.

Danger signs: Eating in response to external cues (TV food commercials, a bad workday, boredom). Regarding one indulgence as blowing diet, and eating more.

Cause: Psychological in origin. Generally affects people who are unhappy with their weight and appearance.

When happens: Can develop at any age; up to 45% of women and 25% of men are trying to lose weight at any given time.

Treatment: Education in nutrition, eating in moderation and regular exercise. Some food restrictions may be necessary for the obese.

Source: Adapted from Los Angeles Times, Oct. 13, 1997.

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