Question 1

A 17-year-old female with anorexia nervosa (BMI 14.8) is admitted for nutritional rehabilitation. She has been restricting intake to fewer than 400 calories per day for the past three months. On admission, her serum electrolytes are within normal limits. On hospital day 3, after initiation of a meal plan providing 1800 kcal/day, she develops tachycardia, confusion, and respiratory distress. Her labs now show: phosphate 1.1 mg/dL (normal 2.5-4.5), potassium 2.9 mEq/L (normal 3.5-5.0), magnesium 1.0 mg/dL (normal 1.7-2.2). What is the most likely diagnosis, and what was the management error?

Accepted Answer

Refeeding syndrome is a potentially fatal complication of nutritional rehabilitation in severely malnourished patients. The key teaching points: (1) Normal electrolytes on admission do not mean the patient is safe - intracellular stores are depleted even when serum levels look normal. (2) Hypophosphatemia is the hallmark of refeeding syndrome. (3) The triad to monitor is phosphate, potassium, and magnesium. (4) Prevention requires starting caloric repletion at a conservative rate, supplementing electrolytes prophylactically, monitoring frequently, and giving thiamine. (5) The sicker the patient, the slower the refeeding.

Question 2

A 22-year-old woman with bulimia nervosa has been in CBT for four months with moderate improvement but continues to binge and purge two to three times per week. Her therapist recommends adding a medication. Which of the following is the best pharmacological choice?

Accepted Answer

Fluoxetine 60mg is the only FDA-approved medication for any eating disorder, and its indication is bulimia nervosa. This is a high-yield board fact. The dose matters: 60mg for BN, not the 20mg starting dose used for depression. Lisdexamfetamine is FDA-approved for BED, not BN - confusing these two indications is a common board trap. Topiramate is off-label for BED. No medication is FDA-approved for anorexia nervosa.

Question 3

A 45-year-old man with obesity (BMI 36) and type 2 diabetes presents for weight management. He describes episodes occurring three to four times per week where he eats large quantities of food rapidly, usually alone, feels unable to stop, and feels intensely ashamed afterward. He does not vomit, use laxatives, fast, or exercise to compensate. He has felt this way for over two years. He says, "I've tried every diet. I just have no willpower." Which of the following best characterizes his condition?

Accepted Answer

The distinguishing criterion between BN and BED is the presence or absence of compensatory behaviors. This patient binges but does not purge, fast, or exercise to compensate - that makes the diagnosis BED, not BN. BED is the most common eating disorder, affects men nearly as often as women, and is dramatically underdiagnosed because clinicians do not screen for it and patients attribute it to willpower failure. Treatment includes lisdexamfetamine (FDA-approved), CBT, and topiramate (off-label). The clinical lesson: when a patient with obesity has repeatedly failed dietary interventions, screen for BED before labeling them non-compliant.

Eating Disorders

Red Flags & Key Clinical Considerations

Refeeding Syndrome in Severe AN

QTc Prolongation in AN and Purging BN

BED Hiding Behind Non-Compliance

Electrolyte Patterns Reveal Purging Method

No FDA-Approved Medication for AN

Related Medications

References & Further Reading