Approach to Eating Disorders - Clinical Notes

Overview

• Goldman-Cecil Medicine, Chapter 200
• Kaplan & Sadock's Synopsis of Psychiatry, Chapter 13
• Harrison's Principles of Internal Medicine 22E

1. Anorexia Nervosa (AN)

Definition / Core Criteria (DSM-5 - all required)

1. Food restriction leading to significantly low body weight
2. Intense fear of weight gain or behaviors persistently preventing weight gain
3. Distorted body image / shape perception, or lack of recognition of the seriousness of low weight

Body image distortion is disturbing when present but is not pathognomonic or invariably required for diagnosis. The central theme is a highly disproportionate emphasis on thinness as a source of self-esteem. - Kaplan & Sadock

Subtypes

• Restricting type - primary behaviors are dieting, fasting, and/or excessive exercise (last 3 months)
• Binge/purge type - recurrent binge eating or purging (last 3 months), includes self-induced vomiting, laxatives, diuretics

Epidemiology & Risk Factors

• Predominantly affects girls and young women in affluent societies; rare in males (~1:10 ratio)
• Onset typically shortly after puberty (seldom after age 30)
• Rare in Asian and African American women
• Risk factors: high concordance in monozygotic twins (genetic component), prior obesity in childhood, sociocultural norms valorizing thinness, stressful life events (leaving home, family disruption)
• Neurobiology under ongoing study

Clinical Features

• Obsessive refusal to eat; food hidden rather than consumed
• Self-induced vomiting, laxative abuse
• Hyperactivity / excessive ritualistic exercise
• Cheerful indifference to emaciation ("la belle indifférence")

• Severe emaciation (often >30% body weight lost by time of presentation)
• Bradycardia, hypotension (markers for hospitalization)
• Lanugo hair on face, body, limbs
• Thin, dry, inelastic skin; brittle nails
• Dental enamel erosion
• Normal pubic hair and breast tissue (distinguishes from hypopituitary cachexia / Simmonds disease)
• Minimal neurological signs of nutritional deficiency despite severity

• Amenorrhea - practically universal; may precede extreme weight loss
• LH reduced to pubertal/prepubertal levels; clomiphene fails to stimulate LH rise
• Low T3 and T4; reverse T3 normal or elevated; TSH normal
• Low basal metabolic rate
• Cortisol usually normal; reduced 17-hydroxysteroid excretion
• Suggests hypothalamic-pituitary dysfunction, but likely secondary to starvation

• ECG changes: T-wave flattening/inversion, ST depression, prolonged QT interval
• ST/T changes usually secondary to electrolyte disturbances
• Hypokalemia can be fatal

• Slight to moderate enlargement of lateral and third ventricles (reversible with recovery)

Medical Complications (Kaplan & Sadock Table 13-2)

2. Bulimia Nervosa (BN)

Definition / Core Features

• Recurrent episodes of binge eating (large amounts of food in a discrete period, sense of loss of control)
• Recurrent compensatory behaviors to prevent weight gain: purging (vomiting, laxatives, diuretics, enemas), fasting, or excessive exercise
• Self-evaluation unduly influenced by body weight/shape
• Most patients are of normal weight (distinguishes from AN binge/purge type)

Epidemiology

• Develops during late adolescence or early adulthood
• More common than AN; affects ~1-3% women

Clinical Features

• Dental enamel erosion from vomiting
• Salivary gland hypertrophy (parotid enlargement)
• Gastric acid reflux, dyspepsia, dysphagia
• Hypokalemic metabolic alkalosis from self-induced vomiting
• Metabolic acidosis with hypokalemia from laxative abuse (bicarbonate loss)
• Dehydration; hypomagnesemia; hyperamylasemia
• Menstrual irregularities in some patients
• Hypotension, bradycardia in some patients
• Thyroid function usually intact; may show non-suppression on dexamethasone suppression test

Key Distinction from AN

• Weight is typically normal or above normal
• Even normal-weight patients should have electrolytes checked if purging

3. Binge-Eating Disorder (BED)

Definition

• Recurrent binge eating episodes with marked distress
• No regular compensatory behavior (distinguishes from BN)
• Binge episodes: eating much more rapidly than normal, eating until uncomfortably full, eating large amounts when not hungry, eating alone due to embarrassment, feeling disgusted/depressed/guilty afterward

Epidemiology

• Often manifests in adulthood; adolescents also affected
• Weight frequently in overweight/obese range
• Most common eating disorder overall

Psychiatric Comorbidities

• Major depressive disorder, anxiety disorders, substance use disorders, disruptive behavioral disorders
• Presence of binge eating after bariatric surgery predicts less weight loss or more weight regain

4. Avoidant/Restrictive Food Intake Disorder (ARFID)

• Restricted food intake not driven by fear of weight gain or body image disturbance
• May develop nutritional deficiencies and, if significantly underweight, complications similar to AN
• Often develops in childhood; may persist into adulthood
• Treatment: behavioral interventions; weight restoration if underweight

5. Other Specified Eating Disorders

• Atypical AN: core symptoms present but weight not abnormally low
• Night-eating syndrome: onset late teens to late 20s; associated with poor sleep, diabetes, obesity, hypertension, cardiovascular disease risk
• Pica: eating non-food substances; associated with zinc/iron deficiency, intellectual disability; complications include poisoning, intestinal obstruction, bezoars
• Rumination disorder: repeated regurgitation; often in intellectual disability; extreme cases cause emaciation

6. Differential Diagnosis

For AN weight loss:

• Medical causes: malignancy, brain tumor, GI disease (IBD, malabsorption), hyperthyroidism, Addison's disease
• Psychiatric: depression (key differences below), somatization disorder, OCD
• Endocrine: hypopituitary cachexia / Simmonds disease (pubic hair/breast tissue preserved in AN)

AN vs. Depression:

7. Investigations

• FBC, electrolytes (K+, Mg2+, Phosphate), urea, creatinine
• LFTs, amylase
• Glucose, thyroid function (TFTs)
• ECG (QTc, arrhythmias)

• Bone densitometry (DEXA) - osteoporosis risk
• LH, FSH (low in AN)
• Reverse T3 (elevated)
• Cortisol

• Electrolytes critical (hypokalemia, alkalosis vs. acidosis depending on purging method)
• Amylase (elevated with parotid hypertrophy)

8. Indications for Hospitalization (AN)

• Bradycardia
• Significant hypotension / orthostatic changes
• QTc prolongation / arrhythmia
• Severe electrolyte disturbance
• Refusal to eat / rapidly declining weight
• Failure of outpatient management
• Medical instability

9. Treatment

9a. Anorexia Nervosa

• Severely underweight patients require inpatient medical monitoring and supervised nutritional rehabilitation
• Higher-calorie refeeding is superior to lower-calorie refeeding both acutely and at 1 year
• Monitor for refeeding syndrome (hypophosphatemia, hypomagnesemia, hypokalemia)
• Optimal setting (inpatient vs. residential vs. outpatient) unclear for non-severe cases; cost plays a role

• Family-based therapy (FBT / Maudsley approach) - especially effective for pediatric/adolescent patients in early phase; involves joint family sessions and independent patient/family intervention
• Individual CBT, interpersonal therapy, cognitive approaches also used
• Comprehensive treatment plan including individual AND family therapy recommended

• SSRIs: not effective in AN (underweight state reduces efficacy)
• Olanzapine (atypical antipsychotic) 2.5-10 mg/day - associated with modest weight gain; currently best evidence for pharmacotherapy in AN
• Cannabinoids as appetite stimulants: results inconclusive
• Neuromodulation (TMS, tDCS, deep brain stimulation): currently under investigation

9b. Bulimia Nervosa

• Cognitive-behavioral therapy (CBT) - treatment of choice; targets binge-purge cycle, distorted cognitions about food/body
• Interpersonal psychotherapy (IPT) - effective, especially for CBT non-responders

• Fluoxetine 60 mg/day - FDA-approved for BN; SSRIs reduce binge-purge frequency
• Topiramate 25-400 mg/day - consistently reduces binge eating but cognitive side effects limit use
• Combined CBT + medication > medication alone

9c. Binge-Eating Disorder

• CBT (face-to-face preferred over internet-based) - reduces binge episodes, body image concerns, prevents weight gain
• IPT - effective
• Behavioral weight loss - first-line
• CBT-guided self-help useful when specialist care unavailable

• Lisdexamfetamine (LDX) 50 or 70 mg/day - only FDA-approved medication for BED in adults; reduces binge episodes, modest weight loss
• Fluoxetine 60 mg/day - reduces binge frequency
• Topiramate 25-400 mg/day - reduces binge frequency; cognitive side effects

Recent evidence (2025): GLP-1 agonists are being investigated for eating disorders - a 2025 systematic review and meta-analysis (PMID: 39891848) examined their impact across eating disorder subtypes.

9d. ARFID, Pica, Rumination Disorder

• Behavioral interventions are the mainstay
• Weight restoration for underweight individuals
• Limited controlled trial evidence

10. Prognosis

Anorexia Nervosa

• Worst prognosis of all eating disorders
• Mortality: up to 6x higher than general population - highest mortality rate of any psychiatric illness
• ~30-50% achieve full recovery; 10-20% remain chronically ill; remainder improve partially
• ~1 in 5 deaths due to suicide; majority due to medical complications
• Better prognosis predictors: adolescent onset, shorter duration of illness, full weight restoration before discharge, weight maintenance in first month post-discharge, dietary variety and energy density before discharge

Bulimia Nervosa

• Higher rates of partial and full recovery than AN
• Treated patients fare significantly better than untreated
• Rapid symptom reduction in early treatment predicts better outcomes

Binge-Eating Disorder

• Relatively better long-term outcomes
• By 5 years, fewer than 1 in 5 community patients still had clinically significant symptoms in one prospective study
• Severe obesity is a long-term risk in >3% of patients

11. Prevention

• The USPSTF found insufficient evidence to recommend universal screening of adolescents and adults not known to be at high risk
• Some professional societies recommend screening as part of comprehensive evaluation
• Interactive, multi-session programs targeting adolescent girls are more effective than universal one-time educational programs

Key Drug Summary Table