Anorexia nervosa
Anorexia nervosa is restriction of energy intake driven by an intense fear of weight gain and a distorted body image, producing a body mass index below 18.5 kg/m2 with bradycardia, hypotension, hypothermia, amenorrhea, and osteoporosis. Diagnosis is clinical; management starts with medical stabilization and slow, monitored nutritional rehabilitation to avoid refeeding syndrome, followed by family therapy in adolescents, with olanzapine as adjunctive pharmacotherapy and bupropion avoided for its seizure risk.
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What this article covers
- Overview
Definition: anorexia nervosa is restriction of caloric intake relative to metabolic requirements, driven by intense fear of weight gain and a distorted body image, producing a body mass index (BMI)…
- Epidemiology
Sex and age distribution: most common in young women, affected 3 to 4 times more often than men; onset is usually in adolescence or young adulthood.
- Risk factors
Female sex: the single strongest demographic risk factor.
- Pathophysiology
Starvation-driven hypometabolic state: chronic caloric restriction shifts the body toward energy conservation, producing bradycardia, hypotension, hypothermia, and slowed gastrointestinal motility.
- Clinical features
Diagnostic criteria: restriction of energy intake leading to a low body weight (BMI below 18.5 kg/m2), an intense fear of gaining weight or persistent behavior that prevents it, and a disturbed body…
- Differential diagnosis
Bulimia nervosa: binge eating with compensatory purging at least weekly for 3 months, but weight is normal or above (BMI above 18.5 kg/m2), unlike anorexia nervosa's low weight.
- Diagnosis
The diagnosis is clinical: confirmed by the triad of low body weight (BMI below 18.5 kg/m2) from restricted intake, intense fear of gaining weight or behavior that prevents it, and disturbed body…
- Management
First, triage for hospitalization: admit for severe underweight, significant electrolyte abnormalities, AKI, or vital sign instability (marked bradycardia, orthostatic hypotension, hypothermia); this…
- Complications
Refeeding syndrome: the most dangerous complication of treatment itself; sudden caloric reintroduction spikes insulin, driving potassium, magnesium, and phosphate into cells and producing…
- Prognosis
Mortality exceeds 10% from suicide or medical complications, the highest lethality of any psychiatric diagnosis.
- Prevention
Identify refeeding risk before nutrition is advanced: major risk factors are BMI below 16 kg/m2, weight loss greater than 15% in the preceding 3 to 6 months, little intake for more than 10 days, and…
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