Essential features and diagnostic criteria ( Fig. 27.1 ):

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  Restriction of energy intake relative to requirements, leading to a significantly low body weight

  
  

  The World Health Organization (WHO) and Centers for Disease Control (CDC) consider a body mass index (BMI) of ≤17 kg/m ² to indicate significantly low weight. An adult with BMI ranging between 17 and 18.5 kg/m ² or even >18.5 kg/m ² (lower limit of normal weight in adults) might be considered to have a significantly low weight if supported by clinical history or other physiologic information. For children and adolescents, a BMI below the 5 ^th percentile suggests that the individual is underweight.

  
  
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  Intense fear of gaining weight or becoming fat that is not alleviated by weight loss.

  
  
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  Disturbance in the way in which one’s body weight or shape is experienced.

Anorexia nervosa: a psychoneurotic disorder.

Severity (based on BMI):

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  Mild: ≥ 17 kg/m ²

  
  
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  Moderate: 16–16.99 kg/m ²

  
  
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  Severe: 15–15.99 kg/m ²

  
  
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  Extreme: <15 kg/m ²

Characteristics : Strong need for control, concrete thinking, limited social spontaneity, perfectionism, and preoccupation with and/or restriction of food ( Fig. 27.2 )

Distorted body image.

Comorbidity: Depressive, obsessive-compulsive, personality, bipolar, and anxiety disorders

For more information, see American Psychiatric Association DSM-5 Guidelines.

Cardiovascular:

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  Hypotension and bradycardia:

  
  
  
  
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    Systolic blood pressures as low as 70 mmHg

    
    
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    Sinus bradycardia: HR as low as 30–40 beats/minute

    
    
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    Attributed to decrease in basal metabolic rate

  
  
  
  
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  Arrhythmias, EKG:

  
  
  
  
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    Sinus bradycardia

    
    
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    ST-segment elevation

    
    
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    T-wave flattening

    
    
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    Low voltage

    
    
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    Long QT interval increases the risk of sudden death

  
  
  
  
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  Cardiomyopathy: from aggressive refeeding or ipecac use

Endocrine and Metabolic:

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  Amenorrhea: Results from disorders in the hypothalamic–pituitary–ovarian axis ( Fig. 27.3 ). Levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are low despite low levels of estrogen. Marginal energy intake coupled with high energy expenditure due to intense physical activity may result in neuroendocrine adaptations, leading to an overall metabolic deficit. Leptin and ghrelin levels may be important indicators of nutritional status; may contribute to functional hypothalamic amenorrhea

  
  

  
  

  
  

  

  
  

  
  

  Osteoporosis associated with amenorrhea.

  
  
  
  
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  Serum chemistry: Hypokalemia, hyponatremia, hypomagnesemia, hypophosphatemia (particularly with refeeding), hypercholesterolemia, and elevation of hepatic enzymes

  
  
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  Euthyroid sick syndrome: Decrease in T3/T4 levels; no treatment is required

  
  
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  Osteopenia/osteoporosis: Undernutrition and its metabolic consequences directly reduce bone turnover and bone formation. Estrogen deficiency is only one factor that contributes to bone loss by inhibiting osteoclastic bone resorption. In addition, low BMI is the consequence of decreased lean muscle mass, low insulin-like growth factor-1 (IGF-1), relative hypercortisolemia, and alterations in hormones impacted by energy availability—specifically higher leptin and lower ghrelin levels. Some improvement in bone mineral density (BMD) occurs with weight gain and resumption of menses, but the rate is lower than that in normal-weight, age-matched controls, and “catch-up” does not always occur.

  
  
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  Hypothermia

  
  
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  Hypoglycemia

  
  
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  Decreased resting energy expenditure

Gastrointestinal: Constipation, delayed gastric emptying, and decreased intestinal motility

Hematologic: Anemia, leucopenia, and thrombocytopenia

Integumentary: Dry skin and hair and lanugo

Neurologic: Cerebral atrophy and ventricular enlargement

Reproductive: Infertility or low-birth-weight infant

Essential features and diagnostic criteria:

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  Recurrent episodes of binge eating: characterized by both of the following:

  
  
  
  
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    Eating, in a discrete period of time (e.g., within a 2-hour period), an amount of food that is definitely larger than what most individuals would eat in a similar period of time

    
    
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    A sense of lack of control over eating during the episode

  
  
  
  
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  Recurrent, inappropriate compensatory behaviors to prevent weight gain: self-induced vomiting; laxative misuse, diuretics, or other medications; fasting; and excessive exercise

  
  
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  On an average, both binge eating and inappropriate compensatory behaviors occur at least once a week for 3 months.

  
  
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  Self-evaluation is unduly influenced by body shape and weight.

  
  
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  The disturbance does not exclusively occur during episodes of AN.

  
  
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  Severity:

  
  
  
  
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    Mild: An average of 1–3 episodes of inappropriate compensatory behaviors per week

    
    
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    Moderate: 4–7 episodes/week

    
    
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    Severe: 8–13 episodes/week

    
    
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    Extreme: ≥14 episodes/week

  
  

Characteristics : In general, normal weight but may be slightly overweight or underweight; individual may conceal food or hoard food for binges, usually secretive, either planned or spontaneous; low self-esteem, anxiety/depressive symptoms, and substance abuse

Comorbidity: Mood and bipolar disorders; personality disorders, specifically borderline personality disorder; substance abuse/dependence; and increased incidence of attempted suicide, stealing/kleptomania, and promiscuity

For more information, see American Psychiatric Association DSM-5 Guidelines.

Cardiovascular: Arrhythmias and hypertension (with diet pills)

Endocrine and metabolic: Menstrual irregularities, less common than in patients with AN ; electrolyte imbalance—compulsive vomiting, hyponatremia, hypokalemia, hypomagnesemia, and metabolic alkalosis; excessive vomiting alone—hypochloremic metabolic alkalosis, which also indicates excessive laxative use

Gastrointestinal: Enlarged salivary glands leading to mildly elevated amylase, constipation, gastritis, esophageal dysmotility patterns (GERD and rarely, Mallory–Weiss or gastric tears), and postbinge pancreatitis

Integumentary: Russell’s sign: scarring and calloused areas on the dorsum of the index and middle finger from self-induced vomiting

Neurologic: Cerebral hemorrhage (with diet pills)

Orofacial: Dental caries, dental erosion, and enlarged parotid glands

Respiratory: Pneumomediastinum

Recurrent episodes of binge eating as described under BN.

The binge eating episodes are associated with three or more of the following patterns:

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  Eating much more rapidly than normal

  
  
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  Eating until feeling uncomfortably full

  
  
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  Eating large amounts of food when not feeling physically hungry

  
  
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  Eating alone because of feeling embarrassed by how much one is eating

  
  
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  Feeling disgusted with oneself, depressed, or very guilty afterward

Marked distress regarding the binge

On an average, the binge occurs at least once/week for 3 months.

The binge is not associated with recurrent, inappropriate compensatory behavior.

For more information, see American Psychiatric Association DSM-5 Guidelines.