Anorexia nervosa vs Bulimia nervosa
How to tell Anorexia nervosa and Bulimia nervosa apart when a board question makes them look alike.
Step 2 CK pairs are in open beta while clinical review finishes. Spot an issue? Tell us.
Objectively low body weight is the fastest discriminator, because bulimia usually occurs at near-normal weight.
Side by side
Significantly low body weight with intense fear of weight gain and persistent caloric restriction points to anorexia nervosa.
Recurrent binge eating followed by compensatory purging in a patient whose weight is often normal points to bulimia nervosa.
Starvation physiology from sustained energy restriction drives endocrine suppression, bradycardia, and multisystem complications.
Repetitive binge and purge cycles cause metabolic and electrolyte shifts despite less sustained caloric deprivation.
BMI <18.5 kg/m2 or weight <85% expected, often with bradycardia <50/min, orthostatic drop >20 mm Hg systolic, low estradiol, and possible leukopenia.
Hypokalemic hypochloremic metabolic alkalosis is common with K+ <3.5 mEq/L, Cl- <98 mEq/L, HCO3- >28 mEq/L, and salivary amylase elevation after frequent vomiting.
The trap
Purging behavior can occur in both disorders, so anchoring on vomiting alone causes misses. The resolving clue is weight status plus medical instability signs such as severe bradycardia or orthostasis that push toward anorexia with urgent stabilization.
The repair move
Next best step: assess medical instability first with orthostatic vitals, ECG, and electrolytes. Admit for monitored nutritional rehabilitation and electrolyte repletion when severe bradycardia, hypotension, or significant orthostasis is present. Start supervised refeeding at about 1200 to 1600 kcal/day with thiamine 100 mg daily and increase calories gradually while checking phosphorus, magnesium, and potassium daily to prevent refeeding syndrome.
Try a free question
CoreA 20-year-old woman has restrictive eating, amenorrhea, and dizziness on standing. BP is 86/54, HR is 48, BMI is 16.0 kg/m2, and potassium is 3.0 mEq/L. What is the next best step in management?
Show answer and explanation
Answer: B. Inpatient medical stabilization with monitored refeeding. Hemodynamic instability with severe underweight status requires inpatient medical stabilization before routine outpatient psychiatric management.
Why the other choices are tempting
- A. Therapy is important long term, but orthostatic hypotension, bradycardia, and hypokalemia require immediate medical admission first.
- C. An SSRI may help comorbid mood symptoms later, but it does not address the immediate cardiovascular and electrolyte risk.
- D. Abrupt full-calorie feeding increases refeeding risk; calories should be advanced in a controlled monitored protocol.
- E. Delaying intervention is unsafe in a medically unstable patient with starvation physiology.
Flashcards
Tap a card to flip it.
Which bedside finding most strongly favors anorexia nervosa over bulimia in a patient with purging behavior?
Objectively low body weight, such as BMI below 18.5 kg/m2, strongly favors anorexia nervosa.
What electrolyte pattern is most typical after frequent self-induced vomiting in bulimia nervosa?
Hypokalemic hypochloremic metabolic alkalosis, often with elevated bicarbonate.
Quick answers
What is the fastest way to tell Anorexia nervosa from Bulimia nervosa?
Objectively low body weight is the fastest discriminator, because bulimia usually occurs at near-normal weight.
What is the key clue for Anorexia nervosa?
Significantly low body weight with intense fear of weight gain and persistent caloric restriction points to anorexia nervosa.
What is the key clue for Bulimia nervosa?
Recurrent binge eating followed by compensatory purging in a patient whose weight is often normal points to bulimia nervosa.
What is the common trap with Anorexia nervosa vs Bulimia nervosa?
Purging behavior can occur in both disorders, so anchoring on vomiting alone causes misses. The resolving clue is weight status plus medical instability signs such as severe bradycardia or orthostasis that push toward anorexia with urgent stabilization.