Monday, May 29, 2023

Anorexia Nervosa

Practice Essentials

Anorexia nervosa (AN) is a potentially life-threatening eating disorder characterized by the inability to maintain a minimally normal weight, a devastating fear of weight gain, relentless dietary habits that prevent weight gain, and a disturbance in the way in which body weight and shape are perceived.

Signs and symptoms

Vital sign changes found in patients with anorexia nervosa include hypotension, bradycardia, and hypothermia. Other changes include the following:

Dry skin


Lanugo body hair


Atrophy of the breasts

Swelling of the parotid and submandibular gland

Peripheral edema

Thinning hair

Patients with purging behavior may have callouses to the dorsum of their dominant hand and dental enamel erosion.

Characteristic signs of inadequate energy (caloric) intake observed in patients with anorexia nervosa that are due to starvation-induced changes include the following:



Resting bradycardia (resting heart rate often 40-49 beats per minute)


Orthostatic lowered blood pressure or pulse

Loss of muscle mass

Low blood glucose (impaired insulin clearance)

Low parathyroid hormone levels

Elevated liver function

Low white blood cell (WBC) count

Behaviorally, a patient may demonstrate a flat affect and display psychomotor retardation, especially in the later stages of the disease.

See Clinical Presentation for more detail.

Some patients who deny a desire to be thin may meet criteria for Avoidant-Restrictive Food Intake Disorder (ARFID).


Because an eating disorder is a clinical diagnosis, no definitive diagnostic tests are available for anorexia nervosa. However, given the multi-organ system effects of starvation, a thorough medical evaluation is warranted. Basic tests include the following:

Physical and mental status evaluation

Complete blood count (CBC)

Metabolic panel


Pregnancy test (in females of childbearing age)

Rapid Diagnosis

Rapid diagnosis of anorexia nervosa is crucial to recovery and in some cases can prevent mortality as delay of treatment with persistent starvation from abnormal eating behavior results in treatment resistance due to the neuroadaptive changes, especially increases in angiopoetin-like protein 6 (ANGPTL6), that occur that increase the likelihood that AN will become chronic and persistent.

Electrocardiogram (ECG)

Gastrointestinal signs of anorexia nervosa include intestinal dilation from constipation and diminished intestinal motility.

Fecal occult blood may be indicative of esophagitis, gastritis, or repetitive colonic trauma from laxative abuse. Thyroid function tests, prolactin, and serum follicle-stimulating hormone (FSH) levels can differentiate anorexia nervosa from alternative causes of primary amenorrhea.

See Workup for more detail.



The process of refeeding must be undertaken slowly, with modest increases in metabolic demands, in order to avoid refeeding syndrome (which includes cardiovascular collapse, starvation-induced hypophosphatemia, and dangerous fluctuations in potassium, sodium, and magnesium levels). A nutritionist or dietitian should be an integral part of the refeeding plan.

Electrolyte repletion is necessary in patients with profound malnutrition, dehydration, and purging behaviors. Repletion may be done orally or parenterally, depending on the patient’s clinical state.

Psychological therapy

Various psychological therapies have proven helpful in treating patients with anorexia nervosa, including the following:

Individual therapy (insight-oriented)

Cognitive analytic therapy

Cognitive-behavioral therapy (CBT)

Enhanced cognitive-behavioral therapy (CBT-E)

Interpersonal therapy (IPT)

Motivational enhancement therapy

Dynamically informed therapies

Group therapy

Family-based therapy (FBT)

Specialist supportive clinical management (SSCM)

Conjoint family therapy

Separated family therapy

Multifamily groups

Relatives and caregiver support groups

Psychopharmacologic therapy

Evidence regarding the efficacy of medication treatment for eating disorders has tended to be weak or moderate. However, fluoxetine, due to effects on serotonin levels, has been found to be generally helpful in patients with anorexia nervosa who have been stabilized with weight restoration. Psychotherapy with adjunctive low-dose olanzapine may be useful for anorexia nervosa during inpatient treatment, especially in the context of anxiety, obsessive eating-related ruminations, and treatment resistance due to failure to engage.

See Treatment and Medication for more detail.

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