skip to main content

AN vs BN Weight — MRCPsych Paper B MCQ

Instant feedback + full explanation. One question, done properly.

ModerateEating DisordersAN vs BN WeightMRCPsych Paper B

A 22-year-old has recurrent objective binge-eating episodes with loss of control at least weekly for 3 months, followed by self-induced vomiting to prevent weight gain. Their self-evaluation is unduly influenced by weight and body shape. Which additional finding most clearly determines whether this presentation is classified as anorexia nervosa with a binge-eating/purging pattern rather than bulimia nervosa?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Significantly low body weight resulting from weight-control behaviours

The distinguishing feature is significantly low body weight. Anorexia nervosa requires low body weight produced or maintained by restrictive or other weight-control behaviours; binge eating and purging can occur within anorexia nervosa. When the person meets the binge-eating and compensatory-behaviour criteria but is not significantly underweight, bulimia nervosa is the more appropriate diagnosis. Loss of control, overvaluation of weight and shape, and self-induced vomiting occur in both disorders. Age and sex may affect epidemiological likelihood but do not define the diagnosis. Clinically, BMI should not be used alone to determine illness severity, medical risk or eligibility for treatment, but weight status remains central to this particular diagnostic distinction.

Reference: National Institute for Health and Care Excellence. Eating disorders: recognition and treatment (NG69), full guideline, section 6.1, 2017; updated 2020. https://www.nice.org.uk/guidance/ng69/evidence/full-guideline-pdf-161214767896