Category · F50-F59 block
F50 — Eating disorders
Terminology note: Anorexia nervosa and bulimia nervosa are the two named eating disorders in this category. Being underweight is a defining feature of anorexia nervosa, not of bulimia nervosa — bulimia nervosa typically occurs at normal or above-normal body weight, and body weight alone should never be used to rule it in or out.
What is this category?
F50 groups disorders of eating behaviour driven by an overvaluation of body weight or shape. F50.0 (anorexia nervosa) involves deliberate weight loss, an intense fear of weight gain, and a distorted body image, maintained well below a healthy weight. F50.2 (bulimia nervosa) involves recurrent episodes of binge eating followed by compensatory behaviour intended to prevent weight gain (such as self-induced vomiting, laxative misuse, or excessive exercise), typically at a normal or higher body weight. The atypical forms (F50.1, F50.3) apply when most, but not all, of the diagnostic features are present.
Core diagnostic concept
The two anchor eating disorders are distinguished primarily by body weight and the presence or absence of binge eating: anorexia nervosa requires deliberate, sustained low body weight; bulimia nervosa requires recurrent binge-purge cycles and does not require being underweight at all. A learner who assumes low weight is required for any eating disorder will misclassify a normal-weight person with clear binge-purge cycles.
Key diagnostic features
- Anorexia nervosa: deliberately maintained low body weight
- Weight is maintained well below what is healthy for the person's age and height, through restricted eating, excessive exercise, or purging.
- Anorexia nervosa: fear of weight gain and body-image distortion
- An intense fear of becoming fat persists even at a significantly low weight, alongside a distorted perception of one's own body size or shape.
- Bulimia nervosa: recurrent binge eating
- Repeated episodes of eating an objectively large amount of food in a discrete period, with a sense of loss of control over eating during the episode.
- Bulimia nervosa: compensatory behaviour to prevent weight gain
- Binge eating is followed by behaviour intended to counteract the binge and prevent weight gain, occurring recurrently.
- Bulimia nervosa does not require being underweight
- Body weight in bulimia nervosa is typically normal or above normal — a normal or elevated weight is not evidence against a bulimia nervosa classification.
How to weigh evidence
These learning labels are teaching aids, not official ICD-10 terminology (see Sources and Method).
- supports A person at a significantly low body weight who describes an intense fear of weight gain and restricts food intake despite the low weight (anorexia), or a person at a normal weight who describes recurrent binge eating followed by self-induced vomiting or laxative use (bulimia).
- consistent not decisive A person reports 'watching what I eat' and occasional larger meals without any pattern of loss-of-control binge eating or compensatory behaviour.
- raises alternative Weight loss or eating change that is better explained by a diagnosed gastrointestinal or endocrine condition, or by a mood disorder's appetite change.
- contradicts or weakens A single occasion of overeating at a celebration, with no recurrent pattern, no loss-of-control eating, and no compensatory behaviour.
- missing and necessary to ask The person's actual body weight relative to a healthy range, the frequency of any binge or compensatory episodes, and whether a medical cause for weight or appetite change has been considered.
Diagnostic boundary
Anorexia nervosa requires deliberately maintained low body weight with fear of weight gain and body-image distortion; bulimia nervosa requires recurrent binge-purge cycles and is typically seen at normal or above-normal weight — body weight distinguishes the two, but a normal weight never rules out bulimia nervosa.
Full comparisons:
Duration and course
Minimum duration: Not fixed by a single universal threshold; recurrence (of binge-purge cycles for bulimia) and persistence (of low weight and fear for anorexia) are more decisive than a specific duration count.
Course: Can be persistent or relapsing-remitting for either subtype; both can coexist with significant medical complications requiring urgent attention outside this classification's scope.
Included presentations
- Anorexia nervosa: deliberate, sustained low body weight maintained through restriction, excessive exercise, or purging, with intense fear of weight gain and distorted body image.
- Bulimia nervosa: recurrent binge eating with a sense of loss of control, followed by recurrent compensatory behaviour to prevent weight gain, typically at normal or above-normal weight.
- Atypical anorexia nervosa and atypical bulimia nervosa: most, but not all, of the defining features present.
Exclusions and distinguishing presentations
| If this is true instead… | Consider | Why |
|---|---|---|
| Recurrent laxative or other substance misuse for weight control, with no binge eating and no body-image-driven restriction pattern | F55 | Substance misuse alone, without the binge-eating and body-image features that define an eating disorder, is better classified as abuse of a non-dependence-producing substance. |
| Weight or appetite change fully explained by a diagnosed gastrointestinal or endocrine condition | organic medical cause behavioural syndrome capsule | A genuine medical cause for weight or appetite change should be excluded before an eating disorder is diagnosed. |
Four-character subtypes (orientation)
A learner should never use body weight alone to rule out bulimia nervosa — a normal or above-normal weight with clear recurrent binge-purge cycles still supports F50.2, not a lower-priority or dismissed classification.
- F50.0 — Anorexia nervosa
- Deliberately maintained low body weight, fear of weight gain, body-image distortion. (in_depth)
- F50.1 — Atypical anorexia nervosa
- Most, but not all, anorexia nervosa features present. (taught for orientation only, not separately assessed in this pilot)
- F50.2 — Bulimia nervosa
- Recurrent binge eating with compensatory behaviour, typically at normal or above-normal weight. (in_depth)
- F50.3 — Atypical bulimia nervosa
- Most, but not all, bulimia nervosa features present. (taught for orientation only, not separately assessed in this pilot)
- F50.4 — Overeating associated with other psychological disturbances
- Overeating linked to another psychological disturbance, without the full bulimia nervosa pattern. (taught for orientation only, not separately assessed in this pilot)
- F50.5 — Vomiting associated with other psychological disturbances
- Self-induced vomiting linked to another psychological disturbance, without the full bulimia nervosa pattern. (taught for orientation only, not separately assessed in this pilot)
- F50.8 — Other eating disorders
- An eating disorder not matching the named subtypes. (taught for orientation only, not separately assessed in this pilot)
- F50.9 — Eating disorder, unspecified
- An eating disorder identified but without enough information to specify further. (taught for orientation only, not separately assessed in this pilot)
External causes to check first
Categories in this block require that the disturbance is not better explained by another external cause listed below. These short capsules are reminders, not full teaching modules.
External cause capsule — Organic or medical presentations resembling F50-F53
A reminder that an eating change, sleep disturbance, sexual dysfunction, or postpartum mental/behavioural change can instead be caused by a genuine physiological or medical condition (e.g. a gastrointestinal or endocrine disorder producing weight and appetite change, obstructive sleep apnoea producing a sleep complaint, diabetes or a medication side effect producing sexual dysfunction, postpartum thyroiditis producing a mood or behavioural change) rather than being a primary F50-F53 disorder, and that this should be actively considered before a primary F50-F53 classification is settled.
What to check:
- Timing: did the change begin during or shortly after a newly diagnosed medical condition, a new medication, or a physiological event (such as childbirth) with a recognised association with the symptoms described?
- Medical context: is there a known medical, endocrine, gastrointestinal, or neurological condition with a recognised association with the presentation?
- Adequacy of investigation: has an appropriate medical work-up actually been completed, rather than simply not yet undertaken?
- Course after the cause is addressed: a presentation that substantially improves once the medical condition is treated or the medication is changed weighs toward a secondary cause rather than a primary F50-F53 disorder.
A full teaching module on the relevant medical specialty's own diagnostic criteria, or a general medical work-up, both of which are outside this capsule's scope.
Worked example — bulimia nervosa at a normal body weight
A 24-year-old at a body weight within the normal range for her height describes recurrent episodes, several times weekly for the past several months, of eating a large amount of food in under an hour with a feeling that she cannot stop, followed by self-induced vomiting. She reports intense guilt after these episodes and says she does this specifically to prevent weight gain. Her weight has remained stable and unremarkable throughout.
- Step 1 — Note the body weight: within the normal range, not low.
- Step 2 — Identify the eating pattern: recurrent binge eating with a clear sense of loss of control.
- Step 3 — Identify the compensatory behaviour: recurrent self-induced vomiting specifically to prevent weight gain.
- Conclusion — F50.2, Bulimia nervosa — a normal body weight does not rule this out; the recurrent binge-compensate cycle is the decisive feature.
Interactive practice
- Type A Restricting since the summer Recognition / application · Foundation
- Type E A normal weight, but something is wrong Misconception correction · Boundary
- Type B Laxatives, but no binges Boundary discrimination · Transfer
Retrieval prompts
Try answering each of these from memory before revealing where to check. Nothing you think or type here is sent or saved anywhere.
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Explain why a normal body weight does not rule out bulimia nervosa.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
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State the two features that must both be present to support an anorexia nervosa classification.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
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Explain what distinguishes bulimia nervosa's compensatory behaviour from a stand-alone pattern of substance misuse.
Reveal answer location
Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.
These self-checks are a personal study aid only, visible to you on this page for this visit — they are not stored and do not affect your mastery dimensions.
Rapid revision card
F50: Anorexia nervosa requires deliberately maintained low weight with fear of weight gain; bulimia nervosa requires recurrent binge-purge cycles and does not require low weight.
Decisive boundary cues:
- Deliberately maintained low weight, fear of weight gain, distorted body image -> weighs toward F50.0.
- Recurrent binge eating plus recurrent compensatory behaviour, weight normal or above -> weighs toward F50.2.
- Purging behaviour alone, with no binge eating and no body-image-driven restriction -> weighs toward F55 instead.
Duration/course: Recurrence of the pattern matters more than a fixed duration count for either subtype.
Nearest alternatives: f55, f54
Common mistake: Assuming a normal or above-normal body weight rules out an eating disorder, when it is fully consistent with bulimia nervosa.
Retrieval prompt: Is body weight low and deliberately maintained (anorexia), or is there a recurrent binge-compensate cycle regardless of weight (bulimia)?
(or use your browser's print function) Open full-page printable revision view →
Related glossary terms
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Bulimia nervosa
An eating disorder marked by recurrent episodes of binge eating with a sense of loss of control, followed by recurrent compensatory behaviour intended to prevent weight gain (such as self-induced vomiting, laxative misuse, or excessive exercise), typically occurring at a normal or above-normal body weight. Classified under F50.2.
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Binge eating
An episode of eating an objectively large amount of food within a discrete period, accompanied by a sense of loss of control over eating during the episode. Recurrent binge eating followed by compensatory behaviour is central to bulimia nervosa (F50.2).
Source basis
WHO ICD-10 international classification structure and code/title (ICD-10 Browser, 2019 English release).
Original educational synthesis, informed by general published clinical-education understanding of ICD-10 F50-F59; no verbatim CDDG or DCR text is reproduced. See Sources and Method for the full policy.
Last reviewed: 2026-09-16. Full policy: Sources and Method.
Educational resource only. This page and its cases teach ICD-10 classification reasoning using fictional scenarios. It does not diagnose real people and should not be used to assess yourself or anyone else. If you or someone you know is struggling with eating, sleep, sexual, postpartum, or substance-use difficulties, please seek prompt professional evaluation.