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[ MDster Editorial Team ](https://mdster.com/about) · Apr 22, 2026 · 7 min read · 40 [ Reviewed by Dr. Ali Ragab, MBBCH, MSc, MCAI ](https://mdster.com/medical-reviewers/dr-ali-ragab) [Editorial Policy](https://mdster.com/editorial-policy) | [Corrections Policy](https://mdster.com/corrections) [ Board Review ](https://mdster.com/blog?tag=board-review) [ Psychiatry ](https://mdster.com/blog?tag=psychiatry) [ Eating Disorders ](https://mdster.com/blog?tag=eating-disorders) [ DSM-5-TR ](https://mdster.com/blog?tag=dsm-5-tr) ![Eating Disorders and Differential: A High-Yield Psychiatry Guide](https://mdster.com/storage/blog/images/eating-disorders-and-differential-a-high-yield-psychiatry-guide.jpg) Share this article Share this post The dangerous mistake in eating disorders is to diagnose by body size instead of by **motive, behavior, and medical risk**. The patient with bradycardia and rapid weight loss may not look underweight. The patient who vomits after meals may have bulimia, rumination disorder, or a GI condition. If you miss the distinction, you miss the treatment. That is exactly why this topic shows up on boards and why it matters on call. **Anorexia nervosa** carries very high mortality, including death from starvation-related complications and suicide. [\[1\]](#cite-1 "Reference [1]") Start with the diagnostic frame ------------------------------- In interview, sort the case using four questions: **Is there restriction? Is there binge eating with loss of control? Are there compensatory behaviors? Is weight or shape driving the syndrome?** APA recommends that the initial evaluation quantify restriction, bingeing, purging, exercise, weight history, food repertoire, and psychosocial impairment, while also checking vitals, CBC/CMP, and ECG when indicated. Do not trust a normal BMI or normal basic labs to reassure you. [\[2\]](#cite-2 "Reference [2]") DisorderWhat separates it**Anorexia nervosa**Restriction causing significantly low weight, plus fear of weight gain and body-image disturbance; restrictive and binge-purge subtypes exist. [\[3\]](#cite-3 "Reference [3]")**Bulimia nervosa**Recurrent binge eating **plus** compensatory behaviors, with self-evaluation overly tied to weight/shape. [\[3\]](#cite-3 "Reference [3]")**Binge eating disorder**Recurrent binge eating **without** regular compensatory behaviors. [\[3\]](#cite-3 "Reference [3]")**ARFID**Restriction due to sensory issues, low interest, or fear of choking/vomiting—not weight/shape concerns. [\[2\]](#cite-2 "Reference [2]")**Rumination disorder**Repeated, often effortless postprandial regurgitation with rechewing/reswallowing/spitting; commonly mistaken for GERD or bulimia. [\[4\]](#cite-4 "Reference [4]") Anorexia, bulimia, and binge eating: where boards trap you ---------------------------------------------------------- For **anorexia nervosa**, remember the triad: inadequate intake, fear of weight gain, and body-image disturbance. The board trap is **atypical anorexia**: patients can meet the psychopathology of anorexia and still have a normal or high BMI after substantial weight loss. SAMHSA and a systematic review both emphasize that medical instability can occur across weight ranges, and rapid weight loss itself predicts risk. [\[3\]](#cite-3 "Reference [3]") > **Clinical Pearl:** A normal BMI does **not** clear a patient with restrictive eating. If the history includes rapid weight loss, bradycardia, orthostasis, hypoglycemia, or electrolyte disturbance, think medical admission before you think outpatient therapy. [\[2\]](#cite-2 "Reference [2]") APA factors supporting hospitalization include HR below 50 bpm, hypotension, orthostatic changes, hypoglycemia, electrolyte abnormalities, QTc prolongation, BMI below 15 in adults, or major recent weight loss. In adults with anorexia, first-line treatment is **eating-disorder-focused psychotherapy with nutritional rehabilitation**; for adolescents and emerging adults with involved caregivers, **family-based treatment** is recommended. Medication is not the main treatment, and NIMH notes there is still no FDA-approved medication for anorexia nervosa. [\[2\]](#cite-2 "Reference [2]") For **bulimia nervosa**, the decisive feature is compensatory behavior after binge eating. For **binge eating disorder**, the decisive feature is the absence of those behaviors. That sounds simple, but patients blur it: fasting, driven exercise, diuretics, and laxatives all count as compensatory behaviors. APA recommends **CBT plus an SRI, especially fluoxetine 60 mg/day**, for adult bulimia. For BED, APA recommends **CBT or IPT**; if medication is needed, antidepressants or **lisdexamfetamine** are evidence-based options. NICE adds an exam pearl: treatment of BED is aimed at stopping binge eating, **not** making weight loss the immediate therapy target, and active dieting during treatment can trigger binges. **Bupropion is contraindicated in patients with purging behaviors** because of seizure risk. [\[2\]](#cite-2 "Reference [2]") ARFID and rumination: the differential most people miss ------------------------------------------------------- **ARFID** is not anorexia without thinness. The patient restricts intake because food feels unsafe, disgusting, painful, boring, or sensorily intolerable. Ask about choking, vomiting, abdominal pain, reflux, eosinophilic esophagitis, oral-motor issues, transition to solids, and longstanding narrow food repertoire. APA is explicit: ARFID requires that the disturbance not be better explained by anorexia or bulimia and that there be **no disturbance in body-weight or shape experience**. The evidence base for treatment is smaller than for AN/BN/BED, but current practice emphasizes nutritional rehabilitation plus CBT- or family-based approaches tailored to the maintaining mechanism. NIMH also notes there is no FDA-approved medication for ARFID. [\[2\]](#cite-2 "Reference [2]") **Rumination disorder** is a board favorite because it is easy to mislabel as purging. The clue is timing and effort: regurgitation occurs during or soon after meals, is often effortless, and may be followed by rechewing or reswallowing. That is different from the driven, weight-control purging of bulimia and different from nausea/retching-predominant vomiting syndromes. The diagnosis is largely clinical, and first-line treatment is **behavioral therapy with diaphragmatic breathing**, sometimes augmented with CBT-style strategies or biofeedback. [\[4\]](#cite-4 "Reference [4]") Clinical Correlations --------------------- Your psychiatry workup should always include medical triage. Weigh the patient, check orthostatics, look for dehydration and purging, and get an ECG in restrictive disorders or severe purging. Rule out mimics and contributors such as thyroid disease, diabetes, inflammatory bowel disease, reflux, and eosinophilic esophagitis when the story points that way. Also screen for depression, anxiety, OCD, substance use, self-harm, and suicidality; comorbidity is common and changes both risk and treatment planning. [\[2\]](#cite-2 "Reference [2]") Key Takeaways ------------- - Diagnose the **driver** of eating behavior, not just the behavior itself. Weight/shape overvaluation points toward **AN/BN**; sensory or aversive fear points toward **ARFID**. [\[3\]](#cite-3 "Reference [3]") - **BN vs BED** is a compensatory-behavior question. If purging, fasting, or driven exercise is regular, it is not BED. [\[3\]](#cite-3 "Reference [3]") - **Normal weight does not exclude anorexia-level danger**; rapid weight loss can still produce bradycardia, hypotension, and electrolyte risk. [\[5\]](#cite-5 "Reference [5]") - For adult **BN**, think **CBT + fluoxetine 60 mg**; for **BED**, think **CBT/IPT**, with lisdexamfetamine as a medication option in selected adults. [\[2\]](#cite-2 "Reference [2]") - **Rumination disorder** is usually diagnosed from the history and treated behaviorally, especially with diaphragmatic breathing. [\[4\]](#cite-4 "Reference [4]") Conclusion ---------- When the history is confusing, strip it down to motive, binge physiology, compensatory behavior, and medical risk. That is how you separate anorexia, bulimia, BED, ARFID, and rumination disorder—and that is how you keep both the boards and the patient from beating you. Frequently Asked Questions ---------------------------- ### How do I distinguish ARFID from anorexia nervosa in clinic? Ask what the restriction is *for*. In **ARFID**, avoidance is driven by sensory intolerance, low interest, or fear of aversive consequences such as choking or vomiting, and there is no core weight/shape overvaluation. In **anorexia nervosa**, fear of weight gain and body-image disturbance are central. [\[2\]](#cite-2 "Reference [2]") ### Can a patient with a normal BMI still have medically serious anorexia? Yes. Rapid weight loss can produce bradycardia, hypotension, hypoglycemia, and electrolyte abnormalities even when BMI is not low; this is the classic atypical anorexia pitfall. [\[5\]](#cite-5 "Reference [5]") ### What is the most testable difference between bulimia nervosa and binge eating disorder? **Compensatory behavior.** Bulimia nervosa requires recurrent binge eating followed by behaviors such as vomiting, fasting, laxatives, or driven exercise; binge eating disorder does not. [\[3\]](#cite-3 "Reference [3]") ### What treatment point about bulimia is worth memorizing for boards? For adults, APA recommends **eating-disorder-focused CBT plus an SRI**, with **fluoxetine 60 mg/day** the best-supported medication. Also remember that **bupropion is contraindicated** when purging is present because of seizure risk. [\[2\]](#cite-2 "Reference [2]") ### When should rumination disorder move up my differential? Think of it when regurgitation is **effortless**, happens during or soon after meals, and is followed by rechewing, reswallowing, or spitting rather than classic nausea-and-retching vomiting. [\[4\]](#cite-4 "Reference [4]") References (10) ------------------- 1. 1. [ www.nimh.nih.gov/health/publications/eating-disorders ](https://www.nimh.nih.gov/health/publications/eating-disorders) [↩](#cite-ref-1-1 "Back to text") 2. 2. [ www.psychiatry.org/getmedia/97405f0d-1bd4-43d0-abdd-c013fcd8686d/APA-Eating-Disorders-Practice-Guideline-Under-Copyediting.pdf ](https://www.psychiatry.org/getmedia/97405f0d-1bd4-43d0-abdd-c013fcd8686d/APA-Eating-Disorders-Practice-Guideline-Under-Copyediting.pdf) [↩](#cite-ref-2-1 "Back to text") 3. 3. [ library.samhsa.gov/sites/default/files/advisory-eating-disorders-sud-pep25-02-010.pdf ](https://library.samhsa.gov/sites/default/files/advisory-eating-disorders-sud-pep25-02-010.pdf) [↩](#cite-ref-3-1 "Back to text") 4. 4. [ pubmed.ncbi.nlm.nih.gov/30789419 ](https://pubmed.ncbi.nlm.nih.gov/30789419/) [↩](#cite-ref-4-1 "Back to text") 5. 5. [ pubmed.ncbi.nlm.nih.gov/37024943 ](https://pubmed.ncbi.nlm.nih.gov/37024943/) [↩](#cite-ref-5-1 "Back to text") 6. 6. American Psychiatric Association. Practice Guideline for the Treatment of Patients With Eating Disorders. 4th ed. 2023. 7. 7. National Institute of Mental Health. Eating Disorders: What You Need to Know. 8. 8. NICE Guideline NG69. Eating disorders: recognition and treatment. 9. 9. Substance Abuse and Mental Health Services Administration. Evidence-Based Care for Clients With Co-Occurring Substance Use Disorders and Eating Disorders. January 2026. 10. 10. Murray HB, Juarascio AS, Di Lorenzo C, Drossman DA, Thomas JJ. Diagnosis and Treatment of Rumination Syndrome: A Critical Review. Am J Gastroenterol. 2019. 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