Eating Disorders

Eating disorders affect 3-5 million in the US; 86% are diagnosed before the age of 20 and up to 11% of high-school students are affected. More than 90% are female, 95% Caucasian, and 75% have an onset in adolescence. Eating disorders are probably the most frequent causes of undernutrition in adolescents in developed countries, but only a relatively small percentage meet the full Diagnostic and Statistical Manual (DSM) IV criteria for anorexia nervosa (see Table 6), while most cases fall into the more general category eating disorder NOS (not otherwise specified). Bulimia, binge eating, and/or purging are probably much more common than full-blown anorexia nervosa, with some estimates of up to 20-30% of college women in the US, and often occur surreptitiously without telltale weight loss. Lifetime prevalence estimates range from 0.5% to 3% for anorexia nervosa and 1-19% for bulimia. So far eating disorders are considered rare in developing countries, but prevalence often increases dramatically when Western influences such as television advertising are introduced, as was the experience in the South Pacific Islands.

The pathophysiology of anorexia nervosa is not well understood, and there is probably a combination of environmental and psychological factors with a biochemical imbalance of neurotransmitters,

Table 6 DSM-IV criteria for anorexia nervosa

A. Refusal to maintain body weight at or above a minimally normal weight for age and height (e.g., weight loss leading to maintenance of body weight less than 85% of that expected or failure to make expected weight gain during period of growth, leading to body weight less than 85% of that expected)

B. Intense fear of gaining weight or becoming fat, even though underweight

C. Disturbance in the way in which one's body weight or shape is experienced; undue influence of body weight or shape on self-evaluation, or denial of the seriousness of the current low body weight

D. In postmenarchal females, amenorrhea, that is, the absence of at least three consecutive menstrual cycles

Specify types

Restricting type: during the episode of anorexia nervosa, the person does not regularly engage in binge eating or purging behavior (i.e., self-induced vomiting or the misuse of laxatives or diuretics)

Binge-eating-purging type: during the episode of anorexia nervosa, the person has regularly engaged in binge eating or purging behavior (i.e., self-induced vomiting or the misuse of laxatives or diuretics)

especially serotonin and its precursor 5-hyroxyin-dole acetic acid, which tends to be reduced. There is a substantial biologic predisposition to run in families with heritability in twin studies of 35-90%.

Eating disorders should be suspected in any adolescent below normal weight ranges or with recent weight loss, but other medical conditions such as intestinal malabsorption, inflammatory bowel disease, and malignancy should also be considered. It is important to realize that most height and weight charts represent cross-sectional population norms, which may not be as sensitive as longitudinal tracking or height velocity of individuals, since puberty occurs at different ages. For example, a 12-year-old who does not gain weight for 6 months may just be entering puberty, or might be severely affected by growth failure due to a malignancy or inflammatory bowel disease.

Physical signs and symptoms of inadequate caloric intake may include amenorrhea, cold hands and feet, dry skin and hair, constipation, headaches, fainting, dizziness, lethargy, hypothermia, bradycar-dia, orthostatic hypotension, and edema. There is no specific laboratory diagnosis, but there are often endocrine and electrolyte abnormalities especially hypokalemia, hypophosphatemia, and hypochlore-mic metabolic alkalosis from vomiting, which often require careful supplementation.

Treatment may be very difficult and prolonged, often involving behavior therapy and occasionally long inpatient stays in a locked unit with threats of forced nasogastric feeding to maintain weight. There is a high risk of refeeding syndrome with edema, possible arrhythmias, and sudden death from electrolyte abnormalities, so protocols have been developed to provide a slow increase of calories, supplemented by adequate amounts of phosphorus and potassium. The anorexic patient's persistent distorted view of body image reality is very resistant to casual counseling.

The consequences of anorexia nervosa can be quite severe and include menstrual dysfunction, cardiovascular disease, arrhythmias, anemia, liver disease, swollen joints, endocrinopathies, cerebral atrophy, and even sudden death. There is a significant bone loss or osteopenia associated with ame-norrhea and lack of estrogen stimulation, which is not completely reversed even with hormone replacement. Anorexia nervosa is well associated with other psychiatric diagnoses such as depression, anxiety, personality disorders, obsessive-compulsive disorder, and substance abuse, and psychiatric problems often continue to remain an issue even when normal weight is maintained. Prognosis is relatively poor compared to other adolescent medical illnesses, with 33% persistence at 5 years and 17% at 11 years. Six per cent die within 5 years and 8.3% by 11 years.

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