63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

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1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

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7 Chapter 7: Pediatric Health Maintenance & Surveillance

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8 Chapter 8: Behavioral Health & Safety Screening

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9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

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10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

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11 Chapter 11: Adult Cancer Screening: Colorectal, Lung & Prostate

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12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

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13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

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14 Chapter 14: Emergent Cardiovascular Conditions

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16 Chapter 16: Vascular & Thromboembolic Emergencies

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17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

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18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury 18.2 Thunderclap & Acute Severe Secondary Headaches 18.3 Acute Ophthalmologic Emergencies

19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

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22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

24.1 Diabetic Ketoacidosis & Hyperosmolar Hyperglycemic State 24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias 24.3 Severe Calcium Abnormalities & Acute Adrenal Crisis

25 Chapter 25: Hematologic, Urologic & Dental Emergencies

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26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

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28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

28.1 Peripheral Neuropathies: Bell's Palsy, Carpal Tunnel & Radiculopathy 28.2 Acute Tinnitus, Sudden Sensorineural Hearing Loss & Cerumen Impaction 28.3 Acute Dizziness, Benign Paroxysmal Positional Vertigo & Vestibular Neuritis

29 Chapter 29: Acute Upper Respiratory Tract Infections

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30 Chapter 30: Acute Lower Respiratory Infections & Cough

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31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

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32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

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33 Chapter 33: Acute Upper Gastrointestinal Conditions

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34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

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40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

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41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

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42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

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46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

54.1 Medical & Behavioral Management of Obesity & Incretin Mimetics 54.2 Osteoporosis & Metabolic Bone Disease: DEXA, FRAX & Antiresorptives 54.3 Nutritional Deficiencies: Vitamin D, B12, Iron & Malnutrition

55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

Key Takeaways Explain This Topic AI

Anorexia Nervosa (AN) requires restriction of energy intake leading to significantly low body weight (BMI <18.5 kg/m2 in adults or <5th percentile in children), intense fear of weight gain, and distorted body perception; physical findings include cachexia, hypothermia (<35°C), bradycardia (<40-50 bpm), lanugo hair, parotid sialadenosis, Russell sign, and euthyroid sick syndrome.

Indications for immediate medical hospitalization in anorexia nervosa include heart rate <40 bpm, systolic blood pressure <90 mmHg (or orthostatic SBP drop >20 mmHg), body weight <75% of expected (BMI <15 kg/m2), body temperature <35.5°C (96°F), serum potassium <3.0 mEq/L, severe hypophosphatemia, and QTc prolongation (>460 ms).

Refeeding syndrome is a fatal complication triggered by carbohydrate reintroduction in a starved patient; massive insulin release drives phosphate, potassium, and magnesium into cells to power glycolysis and ATP synthesis, causing profound hypophosphatemia, respiratory failure, cardiac arrest, and rhabdomyolysis; prevention requires slow caloric advancement (10-20 kcal/kg/day), frequent electrolyte monitoring, and pre-feeding thiamine administration.

Bulimia Nervosa (BN) features recurrent binge eating with inappropriate compensatory behaviors occurring at least once weekly for 3 months in a normal or overweight patient (BMI ≥18.5 kg/m2; BMI <18.5 defines binge/purge anorexia); high-dose fluoxetine (60 mg daily) is the only FDA-approved medication, while bupropion is STRICTLY CONTRAINDICATED in both bulimia and anorexia due to elevated grand mal seizure risk.

Binge-Eating Disorder (BED) is characterized by recurrent binge eating WITHOUT compensatory purging; first-line therapy is Cognitive Behavioral Therapy (CBT), and lisdexamfetamine (Vyvanse 50-70 mg daily) is the only FDA-approved pharmacotherapy for moderate-to-severe BED.

Last updated: September 2026

Spectrum of Eating Disorders in Primary Care

Eating disorders are severe psychiatric illnesses characterized by persistent disturbances in eating behaviors paired with distressing thoughts and emotions regarding weight, body shape, and food intake. They carry among the highest mortality rates of any psychiatric disorder group, driven by acute medical complications (arrhythmias, refeeding syndrome, metabolic collapse) and suicide. Family physicians serve as the frontline defense in detecting subclinical eating pathology, conducting physical and laboratory risk stratification, preventing life-threatening refeeding complications, and coordinating multidisciplinary outpatient or inpatient care.

Anorexia Nervosa (AN)

Anorexia Nervosa is a life-threatening illness characterized by pathological pursuit of thinness, severe caloric restriction, and profound body image distortion. It predominantly affects adolescent females and young women (female-to-male ratio ~10:1), though it occurs in males, diverse gender identities, and older adults.

DSM-5 Diagnostic Criteria for Anorexia Nervosa

A formal DSM-5 diagnosis requires all three core criteria :

Restriction of Energy Intake : Caloric restriction relative to requirements leading to a significantly low body weight in the context of age, sex, developmental trajectory, and physical health. Significantly low weight is defined as a weight less than minimally normal:

Adults : Body Mass Index ( BMI) < 18.5 kg/m² .

Children & Adolescents : BMI < 5th percentile for age and sex, or a failure to maintain expected growth trajectory.

Intense Fear of Gaining Weight : Intense fear of gaining weight or becoming fat, or persistent behavior that interferes with weight gain, even though at a significantly low weight.

Disturbance in Self-Perception : Disturbance in the way in which one's body weight or shape is experienced, undue influence of body weight/shape on self-evaluation, or persistent lack of recognition of the seriousness of the current low body weight. ANOREXIA NERVOSA SUBTYPES & SEVERITY STAGING

• Diagnostic Subtype Operational Definition & Clinical Characteristics
• ══════════════════════════════════════════════════════════════════════════════════════════════════════
• Restricting Type During the last 3 months, the individual has NOT engaged in recurrent
• episodes of binge eating or purging (self-induced vomiting or misuse of
• laxatives, diuretics, or enemas). Weight loss is accomplished primarily

through dieting, fasting, and/or excessive, compulsive exercise.

• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Binge-Eating / Purging During the last 3 months, the individual HAS engaged in recurrent episodes
• Type of binge eating or purging behavior (self-induced vomiting, laxative abuse,

diuretics, or enemas) WHILE MAINTAINING A SIGNIFICANTLY LOW BODY WEIGHT.

• ══════════════════════════════════════════════════════════════════════════════════════════════════════
• Severity Staging (Adults) • Mild: BMI ≥ 17.0 kg/m²
• Moderate: BMI 16.0 - 16.99 kg/m²
• Severe: BMI 15.0 - 15.99 kg/m²
• Extreme: BMI < 15.0 kg/m² (Immediate Medical Hospitalization Mandatory)
• ══════════════════════════════════════════════════════════════════════════════════════════════════════

Exam Pearl : The presence of amenorrhea was eliminated as an obligate diagnostic criterion in DSM-5. This modification prevents the exclusion of pre-menarcheal girls, postmenopausal women, males, and females taking oral contraceptive pills.

Physical Examination & Clinical Findings

Chronic starvation and purging induce multi-organ physiological decompensation: CLINICAL SIGNS OF ANOREXIA NERVOSA

• Physiological System Clinical Manifestations & Diagnostic Signs
• ══════════════════════════════════════════════════════════════════════════════════════════════════════

Vital Signs • Hypothermia: Core body temperature < 35.0°C (95.0°F).

• Sinus Bradycardia: Resting heart rate < 40-50 beats/min.

• Hypotension: Resting blood pressure < 90/60 mmHg.

• Orthostasis: SBP drop > 20 mmHg, DBP drop > 10 mmHg, or HR rise > 20 bpm.

• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Dermatologic & Hair • Lanugo Hair: Growth of fine, downy, unpigmented hair over back, face, arms

(physiological adaptation to conserve core body heat).

• Xerosis & Hypercarotenemia: Dry, scaly skin; yellow-orange pigmentation of

palms and soles (due to impaired hepatic conversion of carotene to vitamin A).

• Acrocyanosis: Cold, bluish discoloration of hands and feet (peripheral vasoconstriction).

• Brittle nails and diffuse telogen effluvium (hair shedding).

• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Head, Neck & Oral • Salivary Gland Hypertrophy (Sialadenosis): Painless, bilateral enlargement of

parotid and submandibular glands (autonomic stimulation from vomiting).

• Perimylolysis: Severe, smooth erosion of dental enamel on the lingual/palatal

surfaces of maxillary teeth caused by recurrent gastric hydrochloric acid exposure.

• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Extremities • Russell Sign: Calluses, hyperkeratoses, or abrasions on the dorsal surface of

the hand/knuckles from repeated trauma against incisors during manual self-emesis.

• Peripheral Dependent Edema: Starvation hypoalbuminemia, fluid shifts, or refeeding.

• ══════════════════════════════════════════════════════════════════════════════════════════════════════
• Laboratory & Diagnostic Derangements

Starvation and purging alter almost every biochemical and hematologic parameter:

Hematology : Gelatinous marrow transformation (starvation marrow hypoplasia) produces leukopenia with absolute neutropenia (most common), normocytic normochromic anemia, and thrombocytopenia. Pancytopenia resolves completely upon weight restoration.

Endocrine / Metabolic Derangements :

Euthyroid Sick Syndrome (Non-Thyroidal Illness) : Characterized by low total and free T3 , normal-to-low T4, and a normal TSH . This represents an adaptive hypometabolic response to starvation. Levothyroxine replacement is strictly contraindicated , as administering exogenous thyroid hormone induces catabolism and precipitates acute cardiac arrest.

Hypogonadotropic Hypogonadism : Starvation blunts hypothalamic gonadotropin-releasing hormone (GnRH) pulsatility, leading to suppressed luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol/testosterone levels (functional hypothalamic amenorrhea).

Hypercholesterolemia : Total cholesterol and LDL cholesterol are paradoxically elevated due to blunted hepatic catabolism and reduced biliary excretion of cholesterol esters during starvation.

Electrolyte Derangements :

Vomiting / Purging : Hypokalemic, hypochloremic metabolic alkalosis with elevated serum bicarbonate (loss of gastric HCl paired with secondary hyperaldosteronism driven by volume depletion).

Laxative Misuse : Hypokalemic, hyperchloremic normal anion-gap metabolic acidosis (loss of alkaline bicarbonate-rich fluid from the colon).

Excessive Water Loading : Profound dilutional hyponatremia predisposing to cerebral edema and status epilepticus.

Cardiovascular : Electrocardiogram (ECG) reveals sinus bradycardia, low voltage, T-wave flattening or inversion, and dangerous QTc interval prolongation (>460 ms) predisposing to fatal ventricular dysrhythmias (Torsades de Pointes).

Skeletal (Osteopenia & Osteoporosis) : Up to 85% of patients exhibit osteopenia and 40% develop osteoporosis. Driven by hypercortisolemia, IGF-1 deficiency, and sex steroid deficiency. Dual-energy X-ray absorptiometry ( DEXA ) is indicated in any patient with underweight status or amenorrhea persisting ≥6 months . Oral contraceptive pills do NOT restore bone density in anorexia nervosa ; nutritional rehabilitation and spontaneous resumption of menses is the only effective therapy.

Indications for Immediate Medical Hospitalization

The Academy for Eating Disorders (AED) and American Psychiatric Association (APA) mandate immediate inpatient medical admission for patients meeting ANY of the following objective criteria: INDICATIONS FOR IMMEDIATE MEDICAL HOSPITALIZATION

• Clinical Domain Threshold Mandating Immediate Medical Admission
• ══════════════════════════════════════════════════════════════════════════════════════════════════════
• Heart Rate • Resting heart rate < 40 beats per minute
• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Blood Pressure • Systolic blood pressure < 90 mmHg OR Diastolic BP < 60 mmHg
• Orthostatic SBP drop > 20 mmHg, DBP drop > 10 mmHg, or HR rise > 20 bpm
• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Body Weight / BMI • Body weight < 75% of median expected body weight for age/height
• BMI < 15.0 kg/m²
• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Body Temperature • Core body temperature < 35.5°C (96.0°F)
• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Electrolyte Derangements • Serum Potassium < 3.0 mEq/L
• Serum Phosphorus < 2.5 mg/dL
• Serum Magnesium < 1.4 mg/dL
• Severe hyponatremia (< 125 mEq/L) or hypernatremia
• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Cardiac Conduction • QTc interval > 460 ms (males) or > 470 ms (females)
• Sustained cardiac dysrhythmias or AV block
• ──────────────────────────────────────────────────────────────────────────────────────────────────────
• Acute Clinical Status • Acute food refusal, uncontrolled purging, syncope, acute hematemesis
• Acute psychiatric emergency: active suicidality or psychosis
• ══════════════════════════════════════════════════════════════════════════════════════════════════════
• Refeeding Syndrome: Pathophysiology & Prevention Protocol

Refeeding syndrome is a potentially fatal constellation of metabolic and electrolyte shifts occurring when nutrition (specifically carbohydrates) is reintroduced to a severely malnourished, starved patient. PATHOPHYSIOLOGY OF REFEEDING SYNDROME

• Prolonged Starvation ──> Total-Body Phosphate, Potassium & Magnesium Depletion
• (Serum levels falsely normal due to hemoconcentration)
• │
• Reintroduction of Carbohydrates ────┘
• │
• ▼
• Massive Surge in Endogenous Insulin Secretion
• │
• ┌───────────┴───────────────────────────────────────────┐
• │ │
• ▼ ▼
• Intracellular Shifting of Phosphate, Potassium & Mg Renal Sodium & Water Retention
• Required for glycolysis & ADP ──> ATP synthesis (Insulin stimulates renal tubule)
• │ │
• ┌───────────┴──────────────────────────────┐ │
• ▼ ▼ ▼
• PROFOUND HYPOPHOSPHATEMIA Hypokalemia & Hypo-Mg Refeeding Edema
• Severe ATP & 2,3-DPG depletion • Ventricular Arrhythmias • Congestive Heart Failure
• Diaphragmatic Respiratory Failure • Torsades de Pointes • Pulmonary Edema
• Acute Rhabdomyolysis & Seizures • Neuromuscular Tetany • Fluid Overload
• Cardiac Arrest & Death
• The Refeeding Syndrome Prevention & Management Protocol

Pre-Feeding Electrolyte Repletion : Obtain baseline serum phosphorus, potassium, and magnesium. Aggressively replete deficient electrolytes intravenously or orally before initiating caloric intake.

Mandatory Pre-Feeding Thiamine Administration :

Thiamine (Vitamin B1) 100 to 200 mg daily IV or PO must be administered BEFORE feeding begins and continued for at least 3 to 5 days.

Rationale : Thiamine pyrophosphate is an obligate cofactor for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase in carbohydrate glycolysis. Reintroducing carbohydrates in a thiamine-deficient patient precipitates acute Wernicke Encephalopathy (triad: encephalopathy, ophthalmoplegia/nystagmus, ataxia) or wet beriberi (high-output heart failure).

Start Low and Advance Slow :

Initiate caloric intake conservatively at 10 to 20 kcal/kg/day (typically 1,000 to 1,200 kcal/day in adults).

Advance caloric density gradually by 200 to 300 kcal every 2 to 3 days based on clinical stability and daily laboratory values.

Intensive Biochemical Surveillance :

Check serum phosphorus, potassium, magnesium, sodium, and renal function every 12 to 24 hours for the first 7 to 14 days of nutritional rehabilitation.

Bulimia Nervosa (BN)

Bulimia Nervosa is characterized by recurrent cycles of binge eating followed by inappropriate compensatory behaviors designed to prevent weight gain.

DSM-5 Diagnostic Criteria for Bulimia Nervosa

A formal diagnosis requires meeting all five criteria :

Recurrent Binge Eating : Consuming, in a discrete period (e.g., within 2 hours), an amount of food definitely larger than what most individuals would eat in similar circumstances, accompanied by a subjective sense of lack of control during the episode.

Inappropriate Compensatory Behaviors : Recurrent behaviors to prevent weight gain, including self-induced vomiting, misuse of laxatives, diuretics, or enemas, fasting, or compulsive excessive exercise .

Frequency & Duration : Both binge eating and inappropriate compensatory behaviors occur, on average, at least once a week for 3 months .

Undue Influence of Shape/Weight : Self-evaluation is unduly influenced by body shape and weight.

Weight Distinction : The disturbance does not occur exclusively during episodes of anorexia nervosa.

Important

The Critical Weight Threshold Differentiating BN from AN :

Patients with Bulimia Nervosa maintain a normal or above-normal body weight (BMI ≥ 18.5 kg/m²) . If a patient meets all symptom criteria for bulimia but has a BMI < 18.5 kg/m² , the formal diagnosis is Anorexia Nervosa, Binge-Eating/Purging Type , NOT Bulimia Nervosa! Anorexia nervosa always supersedes bulimia nervosa.

• Evidence-Based Treatment of Bulimia Nervosa
• 1. First-Line Psychotherapy: Cognitive Behavioral Therapy (CBT-ED)

CBT for Eating Disorders (CBT-ED) is the non-pharmacologic gold standard , demonstrating the highest rates of binge-purge cessation and long-term maintenance of remission. It targets dysfunctional cognitive dietary restraint, body shape over-evaluation, and emotional triggers for binge episodes.

2. First-Line Pharmacotherapy: High-Dose Fluoxetine

Fluoxetine (Prozac) is the ONLY FDA-approved medication for bulimia nervosa .

Dosing : Titrate to 60 mg orally once daily in the morning . Randomized double-blind trials proved that the standard antidepressant dose (20 mg daily) is clinically ineffective for bulimia; the 60 mg daily dose is required to significantly reduce binge-eating and purge frequency.

3. Strict Black-Box Contraindication: Bupropion in Bulimia & Anorexia

Caution

Bupropion (Wellbutrin) is ABSOLUTELY CONTRAINDICATED in patients with active or historical Bulimia Nervosa or Anorexia Nervosa.

Severe Seizure Risk : Clinical trials and post-marketing safety data demonstrated an unacceptably high incidence of grand mal epileptic seizures in patients with eating disorders receiving bupropion.

Mechanism : Acute starvation, fluid shifts, and electrolyte imbalances (hypokalemia, hypomagnesemia, alkalosis) lower the baseline seizure threshold. Bupropion inhibits neuronal norepinephrine and dopamine reuptake, lowering seizure thresholds in a dose-dependent fashion and triggering life-threatening status epilepticus.

Binge-Eating Disorder (BED)

Binge-Eating Disorder is the most common eating disorder in the United States, affecting 2-3% of adults. It affects males and females more equally than AN or BN (approximately 60% female, 40% male) and is strongly associated with class I-III obesity, metabolic syndrome, major depression, and generalized anxiety.

DSM-5 Diagnostic Criteria for Binge-Eating Disorder

Diagnosis requires all five criteria :

Recurrent Episodes of Binge Eating : Eating in a discrete time period an amount of food definitely larger than normal with a subjective sense of lack of control.

Associated Features (≥ 3 of the following 5) :

Eating much more rapidly than normal.

Eating until feeling uncomfortably full.

Eating large amounts of food when not feeling physically hungry.

Eating alone because of feeling embarrassed by how much one is eating.

Feeling disgusted with oneself, depressed, or very guilty afterward.

Marked Distress : Marked personal distress regarding binge eating.

Frequency & Duration : Occurs, on average, at least once a week for 3 months .

ABSOLUTE ABSENCE OF COMPENSATORY BEHAVIORS : The binge eating is NOT associated with recurrent inappropriate compensatory behaviors (no vomiting, laxative abuse, fasting, or compulsive exercise). DIAGNOSTIC COMPARISON: AN VS. BN VS. BED

• Feature Anorexia Nervosa (B/P) Bulimia Nervosa Binge-Eating Disorder
• ══════════════════════════════════════════════════════════════════════════════════════════════════════════

Body Mass Index (BMI) < 18.5 kg/m² (Underweight) ≥ 18.5 kg/m² (Normal/High) Typically ≥ 25-30 (Overweight/Obese)

• ──────────────────────────────────────────────────────────────────────────────────────────────────
• Recurrent Binge Eating? YES (in B/P subtype) YES YES
• ──────────────────────────────────────────────────────────────────────────────────────────────────
• Compensatory Purging? YES (Vomiting, laxatives) YES (Vomiting, laxatives) NO (STRICTLY ABSENT)
• ──────────────────────────────────────────────────────────────────────────────────────────────────
• Body Image Distortion? PROFOUND / Severe PROFOUND / Severe Distress, but less distortion
• ──────────────────────────────────────────────────────────────────────────────────────────────────
• First-Line Psychotherapy Family-Based / CBT CBT-ED CBT
• ──────────────────────────────────────────────────────────────────────────────────────────────────
• FDA-Approved Medication NONE Fluoxetine (60 mg daily) Lisdexamfetamine (50-70 mg)
• ──────────────────────────────────────────────────────────────────────────────────────────────────
• Strictly Contraindicated Bupropion (Seizure risk) Bupropion (Seizure risk) None specific
• ══════════════════════════════════════════════════════════════════════════════════════════════════════════
• Evidence-Based Treatment of Binge-Eating Disorder
• 1. First-Line Psychotherapy: Cognitive Behavioral Therapy (CBT)

CBT is the established non-pharmacologic first-line treatment for BED, demonstrating superior efficacy in reducing binge frequency, eliminating shame, and promoting dietary regularity. However, CBT alone produces modest weight loss; comprehensive management often incorporates behavioral weight loss programs.

2. First-Line Pharmacotherapy: Lisdexamfetamine (Vyvanse)

Lisdexamfetamine is the ONLY FDA-approved medication for moderate-to-severe Binge-Eating Disorder in adults .

Mechanism : A central nervous system sympathomimetic prodrug of dextroamphetamine. Enhances presynaptic release and blocks reuptake of norepinephrine and dopamine in the prefrontal cortex and hypothalamus, suppressing hunger signaling, reducing binge impulsivity, and promoting executive control over food intake.

Dosing Protocol : Initiate at 30 mg orally once daily in the morning . Titrate by 20 mg weekly increments to the target maintenance dose of 50 to 70 mg daily .

Adverse Effects & Monitoring : Insomnia, dry mouth, decreased appetite, tachycardia, hypertension, and anxiety. Monitor resting blood pressure and heart rate at every clinical encounter. Contraindicated in uncontrolled hypertension, active cardiovascular disease, hyperthyroidism, glaucoma, history of stimulant misuse, or concurrent MAOI use.

3. Second-Line & Off-Label Pharmacotherapies

Topiramate (Off-Label) : An anticonvulsant and GABA modulator that significantly reduces binge frequency and promotes meaningful weight loss. However, clinical utility is limited by adverse effects: cognitive slowing ('dopamax'), somnolence, paresthesias, taste perversion (metallic taste with carbonated drinks), metabolic acidosis, and calcium phosphate nephrolithiasis.

SSRIs (Off-Label; Sertraline, Fluoxetine) : Provide short-term reductions in binge eating and treat comorbid depressive or anxiety disorders, but do not produce sustained long-term weight reduction.

Loading diagram... Eating Disorder Differential Diagnosis and Refeeding Syndrome Protocol