Eating Disorders

How to Cite This Chapter: Drossos A, Couturier J, Katzman DK, Findlay S. Eating Disorders. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. Accessed July 23, 2024.
Last Updated: June 11, 2019
Last Reviewed: June 11, 2019
Chapter Information

Definitions and Clinical FeaturesTop

Eating disorders are severe mental illnesses that include both psychiatric and physical symptoms. They can result in substantial morbidity and mortality. Early identification, treatment, and intervention are critically important.

The essential features of the 5 most common eating disorders are as follows:

1) Anorexia nervosa (AN):

a) Persistent restriction of caloric/food intake, often resulting in significantly low body weight.

b) Intense fear of gaining weight or behaviors that interfere with weight gain.

c) Disturbed body image.

2) Bulimia nervosa (BN):

a) Binge eating episodes.

b) Inappropriate compensatory behaviors (eg, vomiting, fasting, excessive exercise).

c) The binge eating and inappropriate compensatory behaviors both occur, on average, ≥1 a week for 3 months.

3) Binge eating disorder (BED):

a) Binge eating episodes in the absence of inappropriate compensatory behaviors.

b) The binge eating occurs, on average, ≥1 a week for 3 months.

4) Avoidant/restrictive food intake disorder (ARFID): The absence of body image disturbance and at least one of the following: failure to meet appropriate nutrition and/or energy needs resulting in significant weight loss (or failure to gain weight/grow as expected), significant nutritional deficiency, dependence on nutritional supplements or enteric feeding methods, marked interference with psychosocial functioning.

5) Other specified feeding or eating disorders (OSFEDs): A mixture of any of the above symptoms but not meeting the full criteria for AN, BN, or BED.

Epidemiology, Pathogenesis, Natural HistoryTop

The prevalence of AN is approximately 0.3% to 0.4% of the female population and is highest in 15-to-19-year-olds, accounting for 40% of all new cases. Less accurate data are available for males. Clinical samples in adult populations show a female to male patient ratio of 10:1, although the ratio in the general population is likely less extreme. BN is more common than AN, with a prevalence rate around 1%, again with a mainly female predominance. BN typically presents in late adolescence or early adulthood. BED is a new diagnosis in the fifth edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and thus data are more limited, though the prevalence is estimated at about 1.6% in females and 0.8% in males. ARFID is a new diagnostic category. Recent literature from tertiary care pediatric eating disorder programs suggests that its prevalence is up to 14% of patients.

The pathogenesis of all the eating disorders is multifactorial, with developmental, biological, genetic, environmental, and psychosocial contributions. Genetic contributions appear particularly important for AN, with heritability estimates in the range of 50% to 85%. Many brain pathways are likely involved, including those that manage memory, reward, emotions, mood, fear, and attention. Malnutrition itself can alter or worsen cognition and may alter the brain’s normal development when the onset of the eating disorder is in the prepubertal or adolescent years. The hypothalamic-pituitary axis is also affected by malnutrition and impacts various organs. Particularly important is the signaling system involved with hunger, energy intake, and satiety. Some early risk factors for an eating disorder include being anxious, sensitive, obsessive, perfectionistic, impulsive, or difficult to soothe.

AN has the highest mortality rate (10%-20%) of any psychiatric illness, with approximately half of deaths due to medical complications and the other half by suicide. The most common medical complications causing death include cardiac events and electrolyte disturbances. About 50% to 70% of patients with AN will recover, with the remainder experiencing a more chronic course. With BN and BED, a relapsing and remitting course of illness is common. For example, 10 years after initial presentation with BN ~10% of patients still have ongoing and chronic symptoms, 20% have subclinical levels of symptoms, and the remaining 70% have achieved recovery.

Medical EvaluationTop

The following recommendations apply to restrictive eating disorders and other eating disorders with significant purging behaviors.


History should include details of the present illness, with a focus on eating disorder symptoms as well as psychiatric and medical comorbidities:

1) Food/eating patterns, including restriction, fasting, acute refusal, food rituals, food allergies and subjective intolerances, 24-hour dietary recall.

2) Weight changes (amount and rate), highest and lowest weights (dates when these occurred), and thoughts and feelings about body shape, weight, and size.

3) Binging and purging (ask individually about each method of purging, eg, self-induced vomiting, use of ipecac, laxative misuse, diuretic misuse, complementary or alternative medicines, or purposeful omission or misuse of prescription medication for the purpose of weight loss).

4) Exercise, including quantity, quality, frequency, and type.

5) For females: Menstrual history, including menarche, usual pattern, any missed periods, last normal menstrual period, amenorrhea and duration of amenorrhea, menstrual threshold weight (weight at which the individual lost her menstrual period), and contraceptive use.

6) For males: Change in sexual function, including erectile dysfunction, loss of morning tumescence, or nocturnal emissions in teens.

7) Medication use/misuse.

8) Alcohol and substance use history.

9) Developmental and growth history.

10) Screen for psychiatric comorbidities, especially mood and anxiety disorders.

11) Suicide/self-harm and risk assessment.

12) Family history, including eating disorders, other mental illness, substance use, suicide, and medical conditions.

13) Review of systems (Table 1).

Physical Examination

1. Vital signs, including oral temperature and orthostatic vital signs (heart rate and blood pressure).

2. Measurement of weight and height, determination of body mass index (BMI). In children and teens, a growth curve is needed to plot height, weight, and BMI, and to make comparisons with the previous growth pattern.

3. Mental status evaluation (see Psychiatric Examination).

4. Focused physical examination (Table 1).

5. Sexual maturity rating in adolescents (a scale of pubertal development based on secondary sexual characteristics, to be completed by a skilled pediatrician or other qualified clinician).


Diagnostic Tests

1. Blood tests (Table 2).

2. Urinalysis.

3. Electrocardiography (ECG).

4. Consider dual-energy x-ray absorptiometry (DXA) to measure bone mineral density in females with long-standing amenorrhea (eg, >6 months).

Differential Diagnosis

Although most eating disorders are easily diagnosed, other medical and psychiatric conditions should be considered, particularly in patients with atypical presentations. Medical conditions that should be considered include:

1) Inflammatory bowel disease.

2) Irritable bowel syndrome.

3) Celiac disease.

4) Malabsorption.

5) Gastric dysmotility.

6) Gastroesophageal reflux.

7) Pregnancy.

8) Endocrine disorders:

a) Diabetes mellitus.

b) Addison disease.

c) Hyperthyroidism.

9) Other:

a) Central nervous system lesions (eg, vasculitis; hypothalamic/pituitary tumors).

b) Chronic infection (eg, tuberculosis, HIV).

c) Immunodeficiency.

d) Collagen vascular disease.

e) Malignancies.

Clinicians should also consider other psychiatric disorders, including:

1) Mood disorders.

2) Anxiety disorders.

3) Somatic symptom disorder (previously called somatization disorder).

4) Substance use disorders.

5) Psychotic disorders.


Acute Medical Complications

1. Metabolic complications, including hypokalemia as a result of vomiting or hyponatremia as a result of significant water loading, can be life-threatening. A common electrolyte disturbance seen with vomiting is hypochloremic metabolic alkalosis. Misuse of laxatives can also result in metabolic alkalosis, dehydration, and hypokalemia.

2. Dehydration is often secondary to restriction of fluids or vomiting.

3. Cardiovascular complications include ECG changes such as bradycardia, prolonged QTc, and other life-threatening dysrhythmias. Orthostatic heart rate and blood pressure changes are also common. Studies in patients with AN have shown loss of cardiac muscle, decrease in left ventricular wall thickness, and decreased cardiac output.

4. Peripheral edema can be a sign of metabolic abnormalities and refeeding syndrome including congestive heart failure.

5. Refeeding syndrome (see Tenets of Good Patient Care, below).

Chronic Medical Complications

1. Reduced bone mineral density can occur early in the course of the illness.

2. Brain imaging studies have shown grey and white matter reductions during the illness. In some of these studies, full recovery of these changes does not occur with weight restoration (the clinical significance of this finding is unknown).

3. In children and adolescents linear growth and pubertal development can be delayed, impaired, or both.

4. Exposure of the teeth and esophagus to gastric acid can result in dental enamel erosion and esophagitis and/or esophageal spasm, respectively.

5. Hematemesis in patients with BN may be indicative of Mallory-Weiss tears.

6. Binge eating has the potential to cause acute gastric dilatation and possible gastric rupture, although this is rare.

7. BED is associated with obesity, with the inherent increased morbidity and mortality.

Treatment and MonitoringTop

Tenets of Good Patient Care

1. Interdisciplinary team: An interdisciplinary team is critical in the comprehensive treatment (medical complications, nutritional rehabilitation, psychiatric comorbidities) of individuals with eating disorders.

2. General approach to management: The initial goals in the management of an individual with a diagnosis of an eating disorder is nutritional rehabilitation including correction of acute medical complications, promotion of metabolic recovery, and restoration of a healthy body weight (if needed). Timely intervention may prevent long-term complications. The interdisciplinary team will need to decide on the treatment setting that is most appropriate for the individual patient. Various treatment settings for the management of an eating disorder include inpatient, day treatment, outpatient, or residential treatment.

3. General approach to inpatient management:

1) Initial approach:

a) Medical stabilization and nutritional rehabilitation should occur first, on an internal medicine or a pediatric hospital ward, if necessary, with consultation from the psychiatric department, or on a specialized eating disorder unit.

b) If the patient has been admitted to a medical unit, transfer or referral to a specialized eating disorders program should be considered once the individual is medically stable.

c) Voluntary treatment is preferred. However, in some circumstances patients can be treated involuntarily if medical complications pose an immediate risk or if the patient lacks the capacity to consent to treatment due to their psychiatric illness. Consultation with the psychiatric department and adherence to local mental health legislation is necessary in these situations.

2) Medical stabilization and medical monitoring:

a) Monitor orthostatic heart rate and blood pressure daily and as indicated.

b) Continuous cardiac monitoring is preferred in patients who are medically unstable and performed as needed thereafter.

c) Ongoing blood testing including extended electrolytes should be performed daily during the first 4 to 5 days of refeeding. If blood test results are normal thereafter, it can be followed as indicated.

d) Fluid intake and output should be monitored and documented until the patient is medically stable.

e) Initially IV fluids should be used with caution and should not exceed doses of maintenance fluids. Aggressive resuscitation can result in congestive heart failure and edema.

f) New evidence suggests that inpatient nutritional rehabilitation in patients with AN can be more aggressive than previously recommended. Nutrition can be safely initiated at 1500 kcal/d in mildly and moderately malnourished patients and be increased by 250 kcal/d to achieve a daily weight gain of ~0.2 to 0.4 kg/d.Evidence 1Weak recommendation (benefits likely outweigh downsides, but the balance is close or uncertain; an alternative course of action may be better for some patients). Moderate Quality of Evidence (moderate confidence that we know true effects of the intervention). Quality of Evidence lowered due to a small-scale randomized controlled trial (imprecision). Golden NH, Keane-Miller C, Sainani KL, Kapphahn CJ. Higher caloric intake in hospitalized adolescents with anorexia nervosa is associated with reduced length of stay and no increased rate of refeeding syndrome. J Adolesc Health. 2013 Nov;53(5):573-8. doi: 10.1016/j.jadohealth.2013.05.014. Epub 2013 Jul 3. Erratum in: J Adolesc Health. 2014 Jan;54(1):116. PubMed PMID: 23830088.

3) Refeeding syndrome: Refeeding syndrome is a potentially life-threatening issue that can arise during refeeding of a severely malnourished individual. It involves a rapid shift in fluids and electrolytes for which the body cannot compensate. Clinically, refeeding syndrome consists of cardiovascular (congestive heart failure, peripheral and pulmonary edema; vital sign instability), neurologic (delirium), and metabolic complications associated with significant morbidity and mortality. Refeeding hypophosphatemia, the hallmark biochemical feature of refeeding syndrome, has been correlated with the degree of malnutrition on admission.

Close medical monitoring includes, but is not limited to, continuous cardiac monitoring, regular checking of electrolytes and extended electrolytes, and evaluation of mental status. The frequency of blood testing can be adjusted up or down based on clinical judgement.

4) Management of eating disorder behaviors:

a) Close monitoring during meals is very important, resources permitting, to ensure the patient is completing their meals/snacks as prescribed.

b) Support patients by preventing behaviors driven by the eating disorder. For instance, mealtime support conducted by skilled staff or family members (who have been taught the methods of meal support) can be helpful to patients. An example of techniques used in meal support includes distracting the patient with conversation or listening to music, so they are less focused on the food itself. These techniques can be helpful in facilitating the patient to complete their entire meal.

c) Following meals, some patients may experience psychological and physical discomfort. They may be preoccupied with thoughts of purging and feelings of guilt. A period of support and distraction (for 30-60 minutes) following meals with restriction of the use of washrooms can help reduce these thoughts and urges and prevent these behaviors.

d) The activity level of individuals with an eating disorder on the inpatient unit should be kept to a minimum, in an effort to decrease energy expenditure. Initial clinical practice for patients who are medically unstable typically includes a short period of medical bed rest.

e) Physical restraint should be avoided.

f) Laxatives that were regularly used/misused by the patient should not be withdrawn abruptly, as this could cause severe constipation and obstruction.

4. General considerations for outpatient treatment: Psychotherapy:

1) Family-based therapy has the best evidence for adolescents with AN and is recommended as first-line treatment.Evidence 2Strong recommendation (benefits clearly outweigh downsides; right action for all or almost all patients). High Quality of Evidence (high confidence that we know true effects of the intervention). Couturier J, Kimber M, Szatmari P. Efficacy of family-based treatment for adolescents with eating disorders: a systematic review and meta-analysis. Int J Eat Disord. 2013 Jan;46(1):3-11. doi: 10.1002/eat.22042. Epub 2012 Jul 23. Review. PubMed PMID: 22821753. Lock J, Le Grange D, Agras WS, Moye A, Bryson SW, Jo B. Randomized clinical trial comparing family-based treatment with adolescent-focused individual therapy for adolescents with anorexia nervosa. Arch Gen Psychiatry. 2010 Oct;67(10):1025-32. doi: 10.1001/archgenpsychiatry.2010.128. PubMed PMID: 20921118; PubMed Central PMCID: PMC3038846. Family-based treatment may also be helpful for adolescents with BN, although there is less evidence supporting this.

2) Other psychotherapies can be of benefit in BN and BED (eg, cognitive behavior therapy [CBT], interpersonal therapy).

3) Dialectical behavior therapy (DBT) is a specialized form of CBT that integrates mindfulness and acceptance strategies. It is primarily skills-based and can be helpful in those with extensive mood dysregulation, interpersonal difficulties, and impulsive behaviors (including self-harm, substance use, bingeing and purging).

5. Medications:

1) There is little clear evidence for the use of medications to treat the primary diagnosis of an eating disorder, especially for AN. Furthermore, there is even less clarity of evidence for use of medications with children and adolescents.

2) Fluoxetine has been suggested (especially at higher doses, ~60 mg/d) for individuals with BN to target the binge/purge behaviors once the decision to treat with pharmacotherapy has been reached.Evidence 3Weak recommendation (benefits likely outweigh downsides, but the balance is close or uncertain; an alternative course of action may be better for some patients).High Quality of Evidence (high confidence that we know true effects of the intervention). Aigner M, Treasure J, Kaye W, Kasper S; WFSBP Task Force On Eating Disorders. World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for the pharmacologic treatment of eating disorders. World J Biol Psychiatry. 2011 Sep;12(6):400-43. doi: 10.3109/15622975.2011.602720. Review. PubMed PMID: 21961502. We recommend this treatment for at least an additional 6 to 12 months following the cessation of binge/purge symptoms and when there are no ongoing eating disorders/body image cognitive distortions.

3) A low-dose atypical antipsychotic (such as olanzapine 2.5-5 mg or risperidone 0.5-1 mg) can be helpful in patients with severe distress. In our practice severe distress is more commonly seen in patients with AN compared with other eating disorders.

4) Benzodiazepines can also be used for agitation, but we suggest this should be at low doses and should be used minimally and with caution, as they have addiction potential; in younger patients, there is the possibility of a paradoxical reaction whereby the benzodiazepine worsens agitation.


Table 16.11-1. Symptoms, signs, and clinical findings in patients evaluated for eating disorders


Brain (neurologic/psychiatric)

Head and neck

– Weakness, fatigue, lethargy

– Dizziness, syncope

– Weight fluctuations: marked weight loss or gain

– Arrested linear growth

– Cold intolerance

– Sweating/hot flashes

– Poor concentration and memory

– Altered cognition

– Insomnia

– Features of depression, anxiety, obsessive-compulsive disorder

– Social withdrawal

– Irritability

– Dental enamel erosion and caries

– Parotid enlargement (from self-induced vomiting)

– Oral trauma and lacerations

– Dry, cracked lips and tongue

Cardiac and pulmonary



– Dysrhythmias

– Palpitations

– Chest pain

– Shortness of breath

– Edema

– Dizziness

– Orthostatic heart rate and blood pressure changes

– Delayed capillary refill

– Acrocyanosis

– Constipation or diarrhea

– Gastroesophageal reflux

– Abdominal discomfort/bloating

– Delayed gastric emptying, early satiety

– Hemorrhoids, prolapse

– Hematemesis

– Amenorrhea or irregular menses

– Delayed pubertal development

– In diabetes, poor glucose control and possible diabetic ketoacidosis

– Infertility




– Renal calculi

– Edema

– Dehydration

– Incontinence

– Dry skin

– Carotenoderma

– Hair loss or thinning

– Brittle nails

– Lanugo

– Poor wound healing

– Russell sign: calluses on the knuckles or dorsum of the hand due to self-induced vomiting

– Decreased bone mineral density/osteoporosis, risk of bone fractures

– Fatigue

– Muscle weakness

– Cramps

Table 16.11-2. Recommended blood testing in patients evaluated for eating disorders

CBC, differential count

Creatinine and urea

Pregnancy test (in women of childbearing age)

– Electrolytes: Sodium, potassium, chloride, bicarbonate

– Extended electrolytes: Calcium, magnesium, phosphorous

– Glucose

Liver function tests: AST, ALT, ALP, GGT, total protein, albumin, bilirubin


– LH, FSH, and estradiol in patients with amenorrhea

ESR and/or CRP



ALP, alkaline phosphatase; ALT, alanine aminotransferase; AST, aspartate aminotransferase; CBC, complete blood count; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; FSH, follicle-stimulating hormone; GGT, gamma-glutamyl transferase (transpeptidase); LH, luteinizing hormone; TSH, thyroid-stimulating hormone.

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