Bulimia nervosa !

Bulimia is an eating disorder with repeated binge eating followed by vomiting or other purging. Weight is often normal, so it can go unnoticed.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

An eating disorder with recurrent binge eating (a large amount of food with a sense of loss of control) followed by compensatory behaviour such as self-induced vomiting, laxatives, fasting or excessive exercise. Self-worth depends unduly on shape and weight, and body weight is usually normal.

Who gets it

Lifetime prevalence is around 1–2% in young women and lower in men. It usually begins in late adolescence or early adulthood. In Latin America, as elsewhere, it is underdiagnosed because weight is normal and behaviour is hidden; social pressure about thinness is a recognised driver.

Causes

Genetic vulnerability and altered serotonin function in appetite and impulse control
Dieting and restriction that trigger binges in a restrict-binge-purge cycle
Low self-esteem, perfectionism and difficulty regulating emotions
Cultural ideals of thinness

Risk factors

Female sex, adolescence and young adulthood
Childhood obesity or early repeated dieting
Sports or careers that emphasise weight (dance, modelling, gymnastics)
Depression, anxiety, substance use or borderline personality traits
History of trauma or sexual abuse

Pathophysiology

Restriction raises hunger signals from the hypothalamus and lowers inhibitory control, triggering binges; guilt then drives purging, which brings short relief and reinforces the cycle. Repeated vomiting loses stomach acid and potassium, causing hypokalaemic, hypochloraemic metabolic alkalosis; gastric acid erodes tooth enamel, and repeated stimulation enlarges the salivary (mainly parotid) glands. Laxative misuse may instead cause metabolic acidosis.

Classification

Severity by weekly compensatory episodes: mild 1–3, moderate 4–7, severe 8–13, extreme 14 or more
In partial or full remission

Symptoms and signs

Secret binges and frequent trips to the bathroom after meals
Bilateral, painless parotid enlargement ('chipmunk cheeks')
Calluses or scars on the knuckles from inducing vomiting (Russell sign)
Dental enamel erosion, especially the inner surfaces of the upper front teeth; tooth sensitivity
Sore throat, heartburn, bloating, constipation, irregular periods and weight fluctuation within a normal range

Diagnosis

Clinical: DSM-5-TR criteria: recurrent binges and compensatory behaviour at least weekly for three months, self-evaluation unduly influenced by shape and weight, not occurring only during anorexia nervosa. Screening tools such as SCOFF help in primary care; examination looks for parotid swelling, Russell sign, dental erosion and vital-sign changes.
Tests: Electrolytes (low potassium and chloride, high bicarbonate with vomiting), magnesium, phosphate, kidney function and glucose; serum amylase may be raised (salivary origin). ECG for arrhythmia or prolonged QT. Pregnancy test when relevant.
Imaging: Not needed for diagnosis. Chest imaging or endoscopy only if oesophageal injury is suspected.

Differential diagnosis

Anorexia nervosa, binge-purge type (low body weight)
Binge-eating disorder (no compensatory behaviour)
Major depression with appetite change
Gastrointestinal causes of vomiting (e.g. gastric outlet obstruction)
Hypothalamic tumour or Kleine-Levin syndrome (rare)

Goal of treatment

Stop the binge-purge cycle, restore regular eating, correct electrolytes and medical complications, and treat coexisting mood and anxiety disorders, mostly as an outpatient.

Treatment

Conservative: Cognitive behavioural therapy specific for eating disorders (CBT-E) is first-line; family-based treatment in adolescents; nutritional counselling with a regular meal plan.
Medical: SSRIs, with fluoxetine the best studied, reduce binges and purging, often at higher doses than for depression. Bupropion is contraindicated because of seizure risk. Potassium replacement when low.
Acute: Hospital admission for severe electrolyte disturbances, arrhythmia, oesophageal injury, uncontrolled purging or high suicide risk.
Follow-up: Nursing priorities: monitor electrolytes, vital signs and ECG; supervise the period after meals (bathroom access) to prevent purging; dental referral; suicide risk screening.

Complications

Hypokalaemia with cardiac arrhythmia and sudden death
Metabolic alkalosis and dehydration
Oesophagitis, Mallory-Weiss tear and, rarely, oesophageal rupture (Boerhaave syndrome)
Dental erosion and caries
Chronic constipation from laxative misuse; pancreatitis
Depression, substance use and suicide

Prognosis

Better than anorexia nervosa: about half of people recover fully with treatment, though relapse is common under stress. Mortality is raised, mainly from suicide and electrolyte-related arrhythmias.

Prevention

Avoiding weight-focused comments and restrictive dieting in adolescents
Early screening in primary care, schools and sports settings

Test yourself

Think of the answer, then tap the question to see it.

How does bulimia nervosa differ from anorexia nervosa, binge-purge type?

In bulimia body weight is normal or above normal; anorexia requires significantly low body weight.

Which acid-base and electrolyte disturbance does repeated vomiting cause?

Hypokalaemic, hypochloraemic metabolic alkalosis.

What are three classic physical signs of bulimia?

Bilateral parotid enlargement, calluses on the knuckles (Russell sign) and dental enamel erosion.

Which antidepressant is contraindicated in bulimia, and why?

Bupropion, because it lowers the seizure threshold, especially with electrolyte disturbances.

What is the first-line psychotherapy for bulimia nervosa?

Cognitive behavioural therapy adapted for eating disorders (CBT-E).

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Bulimia (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

Hypothalamus highlighted on the Durgical 3D model