• Clinical science

Eating disorders (Feeding and eating disorders)


Eating disorders are psychological conditions characterized by abnormal eating habits, disturbed body image, and, in most of these disorders, weight loss. Adolescent girls and young women are most commonly affected. Individuals with anorexia nervosa are preoccupied with their weight, body image, and a desire to be thin. Self-imposed restriction of calories, excessive exercising, or purging (e.g., laxative use) result in pronounced and potentially fatal weight loss. Bulimia nervosa is characterized by recurrent binge eating followed by measures to compensate for overeating (e.g., self-induced vomiting) driven by a fixation on body weight and shape. However, the BMI in individuals with bulimia is typically normal or elevated. Individuals with binge eating disorder have binge eating episodes but do not take measures to control their weight. Unlike in individuals with anorexia or bulimia nervosa, there is no fixation on body weight and shape, and patients are often overweight. Pica is an eating disorder characterized by the appetite for and ingestion of nonnutritive substances (e.g., hair, clay, mud). First-line treatment for all conditions is cognitive behavioral therapy (CBT). All eating disorders, with the exception of pica, are associated with an increased risk of mood disorders, anxiety disorders, and personality disorders and often have a chronic, relapsing disease course, with various outcomes from complete recovery, symptom fluctuation and relapses to progressive deterioration.

Anorexia nervosa


  • Sex: > (10:1)
  • Peak age: 10–25 years of age


The etiology of anorexia nervosa is multifactorial and not entirely understood. Several factors are thought to contribute to the development of the disease:

  • Genetic factors: There is a higher concordance of anorexia in identical twins than in fraternal twins.
  • Neurobiological factors: a disorder of the endogenous reward system
  • Psychiatric factors: associated with OCD, anxiety disorders, and mood disorders
  • Psychosocial factors
    • Traumatization
    • Poor ability to handle/resolve conflicts
    • Difficulty establishing autonomy and gaining control (e.g., separation from parents)
    • High-pressure careers and sports (e.g., modeling, ballet, gymnastics, wrestling )
    • Unrealistic standards of beauty


  • Significant deliberate reduction in body mass (as measured by BMI) using strategies that include restrictive eating, purging, and excessive exercise.
  • Fear of weight gain motivates compensatory behavior that promotes weight loss, even if the patient already has low body weight.
  • Body image disturbance
    • Excessive concern about weight and body shape, despite being considerably underweight
    • Lack of awareness of the seriousness of low body weight


  • Restricting type
    • No binge eating or purging over a 3-month period
    • Suggests weight loss is achieved by excessive dieting, exercise, or fasting
  • Binge-eating/purging type
    • Presence of binge eating or purging over a 3-month period
    • Suggests weight loss is achieved by vomiting, diuretic and laxative abuse, or enemas

Severity based on BMI

  • Patients ≤ 20 years of age: BMI below the 10th percentile for sex and age is considered the threshold for being underweight.
  • Patients > 20 years of age
    • Mild: BMI 17–18.4 kg/m2
    • Moderate: BMI 16–16.99 kg/m2
    • Severe: BMI 15–15.99 kg/m2
    • Extreme: BMI < 15 kg/m2

Other clinical features


Laboratory findings normalize following adequate treatment and weight gain!



Individuals with eating disorders may switch from one disorder to another or show merging of symptoms, especially following treatment of one disorder!

Anorexia nervosa is associated with a high mortality rate because of associated medical complications (e.g., arrhythmia, bradycardia) and the high rate of suicide among individuals with the disease.


Bulimia nervosa


  • Sex: > (> 90% of affected individuals are young women)
  • Peak age: 20–24 years of age



  • Recurrent binge eating
  • Recurrent compulsive compensatory behavior to counteract weight gain
    • Most frequent: self-induced vomiting after binge eating
    • Laxative abuse
    • Transient starvation periods
    • Other weight-loss measures
  • Binge eating and compulsive compensatory behavior both occur at least once a week over a 3-month period.
  • Sense of self-worth pathologically influenced by the perception of physical appearance (body weight and shape)
  • Binging and purging do not occur exclusively during episodes of anorexia nervosa

Additional clinical features


Treatment should be initiated as early as possible to avoid chronification:


  • The disease course is chronic with relapses.
  • Mortality: 2–8 times higher than the general population
  • Increased risk of psychological comorbidities

Bulimia can transition to anorexia and vice versa!

The antidepressant bupropion lowers the seizure threshold. It is therefore contraindicated in individuals with eating disorders who are at an increased risk of developing seizures secondary to dehydration and electrolyte imbalances.


Binge eating disorder


  • Sex: >
  • Peak age: early adulthood to middle age
  • Prevalence: most common eating disorder in the US (∼ 2–5% of general population)


The etiology of binge eating disorder is multifactorial and not entirely understood. For factors, see also “Etiology” in anorexia nervosa above.

  • Genetic factors (family history is common)
  • Strict dieting and having access to preferred binge foods
  • Psychological issues (e.g., poor body self-image, stress, childhood bullying)


  • Recurrent binge eating: eating a portion of food disproportionately larger than what an average individual would eat in a similar time span (e.g., two hours) and under similar circumstances
  • Feeling of lack of control over amount of food consumed with at least three of the following properties:
    • Eating faster than normal
    • Eating until uncomfortably full
    • Eating large amounts when not hungry
    • Eating alone because of embarrassment regarding eating habits
    • Feeling of disgust and/or guilt after eating
  • Symptoms manifest at least 1/week for 3 months

Additional clinical features



  • Chronic, relapsing disease course
  • Increased risk of psychological comorbidities (e.g., depression)

Individuals with binge eating disorder may be experiencing emotional distress about their binge eating, but not about their weight or appearance!




An eating disorder characterized by the appetite for and ingestion of nonnutritive substances (e.g., hair, clay, soil, ice, paint chips).


  • Prevalence: highest in children, during pregnancy, and in individuals with psychiatric conditions (see “Etiology” below)
  • Sex: =

Etiology [12]

The etiology is not entirely understood. Pica is associated with:


  • Persistent ingestion of nonnutritive substances for > 1 month that is inappropriate for developmental age and not part of culturally or socially normative practice.
  • Possibly, underlying zinc or iron deficiency anemia
  • Complications: e.g., lead poisoning (paint ingestion), GI complications (e.g., bowel obstruction, bowel perforation, bacterial or parasitic infections)

Treatment [12]

  • Behavioral interventions and nutritional rehabilitation (first-line)
  • Pharmacotherapy: SSRIs (second-line)

Pica should be differentiated from nonsuicidal self-injurious or maladaptive behavior of eating harmful objects (e.g., batteries, glass shards, needles) in personality disorders.