Anorexia nervosa

Last updated: July 13, 2023

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Summarytoggle arrow icon

Anorexia nervosa (AN) is a complex eating disorder with a high mortality rate. It is characterized by deliberate restriction of energy intake, resulting in significantly low body weight. Causes are multifactorial and include genetic factors, psychiatric disorders, and psychosocial factors (e.g., trauma). Typical features include body image disturbance and fear of weight gain. There are two subtypes of AN: restrictive (weight loss is achieved by reducing intake and increasing calorie expenditure, e.g., with excessive exercise) and binge eating/purging (if those behaviors are present). Individuals without low body weight but who otherwise meet the diagnostic criteria for AN are diagnosed with atypical AN. It is important to assess for malnutrition severity in affected individuals, regardless of body weight or body mass index (BMI). Diagnostic workup should include evaluation for associated complications (e.g., electrolyte abnormalities) and, in some cases, any underlying conditions that may affect weight or cause a change in eating behaviors (e.g., thyroid disorder). Management should be provided in an outpatient setting if possible, but the presence of red flags in eating disorders may indicate the need for hospitalization for acute stabilization. All patients should be referred for psychotherapy and nutritional management for weight restoration in AN. Pharmacotherapy may be used as adjunctive therapy to help manage comorbid psychiatric conditions (e.g., depression) or promote weight gain in selected patients. AN has the highest mortality rate of all psychiatric disorders because of the high incidence of serious medical complications.

Epidemiologytoggle arrow icon

  • Prevalence [2][3][4]
    • : 0.9–1.4%
    • : 0.1–0.3%
  • Age: Onset usually occurs between ∼ 12 and 25 years of age. [2][5]
  • Sex: > (3–12:1) [2][3][4]

AN is likely underdiagnosed in boys and men, as the condition is more commonly associated with girls and women. [6]

Epidemiological data refers to the US, unless otherwise specified.

Etiologytoggle arrow icon

The etiology of AN is multifactorial and not entirely understood. Several factors are thought to contribute to the development of the disorder:

Clinical featurestoggle arrow icon

  • Most patients present with a low BMI. [14]
  • Associated features of severe malnutrition may be present.
Associated features of severe malnutrition in anorexia nervosa [10][15]
Clinical features
Skin and hair

Patients with AN who engage in purging behavior may also exhibit clinical features of bulimia nervosa such as dental damage, sialadenosis, and Russell sign. [10]

Diagnosticstoggle arrow icon

General principles

DSM-5 diagnostic criteria [5][7][20]

DSM-5 diagnostic criteria for anorexia nervosa [7][20]
  • Deliberate restriction of energy intake, causing significantly low body weight, e.g.: [21]
    • Patients > 20 years of age: BMI < 18.5 kg/m2
    • Patients ≤ 20 years of age: BMI < 5th percentile for sex and age [21][22]
  • ≥ 1 of the following:
    • Intense fear of weight gain
    • Persistent behaviors that interfere with weight gain (e.g., purging, excessive exercise)
  • ≥ 1 of the following:
    • Body image disturbance
    • Disproportionate impact of weight or body shape on self-value
    • Lack of acceptance of the seriousness of current low weight
All criteria must be fulfilled.

Patients who have a normal or elevated BMI but meet all other criteria for AN are diagnosed with atypical AN, which is in the DSM-5 category of Other Specified Feeding and Eating Disorders. [5][9]

Subtypes [5][7][20]

  • Anorexia nervosa, restricting type (ANR)
    • Weight loss is achieved by any of the following:
      • Excessive dieting
      • Exercise
      • Fasting
    • No recurrent binge eating or purging over a 3-month period
  • Anorexia nervosa, binge eating/purging type (ANBP):

Severity [6][7]

Severity of anorexia nervosa in adults [7]
  • BMI ≥ 17 kg/m2
  • BMI 16–16.99 kg/m2
  • BMI 15–15.99 kg/m2
  • BMI < 15 kg/m2

Managementtoggle arrow icon

Approach [9][10][14]

Weight gain may initially worsen the patient's mood and disordered behaviors, though this should improve over time. Counsel patients to anticipate this and monitor them appropriately. [10]

Weight restoration for AN [10][19][23]

Goal weight range [6][10]

  • Individualize the goal for each patient, considering: [10]
    • Weight at which reproductive function is restored (for postmenarchal patients)
    • Growth and pubertal development trajectories in adolescents and young adults
    • Possible initial goal: BMI > 20 kg/m2 for adults
  • During growth periods in children: Reassess goal weight every 3–6 months.
  • Carefully consider if the goal weight should be shared with the patient.

Weigh patients after voiding, with their shoes removed. [10]

Nutritional rehabilitation

  • An individualized diet plan should be created in collaboration with a registered dietitian nutritionist. [10]
  • Patients should be carefully monitored to prevent refeeding syndrome.
  • Weekly weight goals are recommended in addition to a final target weight.
  • Promote healthy eating habits, including:
    • Eating regular meals and snacks
    • Expanding food variety
    • Focusing on food with a high energy density
  • Enteral and parenteral nutrition are avoided, if possible.
Nutritional goals for anorexia nervosa [6][10][19][23]

Inpatient or residential

Caloric intake
  • Initially: 1500–2000 kcal/day [10][14][23]
  • Gradually increase caloric intake (e.g., by 200–500 kcal every 1–3 days) up to 3000–4000 kcal/day. [10][19][23]
  • Consider increasing the patient's current caloric intake by 300–500 kcal every 3–4 days. [23]
Weight gain rate
  • ∼ 1–1.8 kg (2–4 lb)/week [10][23]
  • ∼ 0.25–1 kg (0.5–2 lb)/week; monitor weight gain at least weekly. [10][23]

Early and rapid weight gain are associated with a better prognosis. [10][23]

Psychotherapy [7][9][10]

  • Psychotherapy is often needed for ≥ 1 year. [10]
  • Type of therapy depends on the age of the patient, availability, and patient preference. [10]
Psychotherapy for patients with anorexia nervosa
Therapy types
Adolescents and young adults

Therapy for caregivers (e.g., Experienced Carers Helping Others) improves outcomes for patients with AN. [10]

Pharmacotherapy [7][9][10]

  • Although frequently prescribed, there is limited evidence to support the use of pharmacotherapy in AN. [9]
  • SSRIs have a limited role.
    • Not effective if prescribed solely for the management of AN
    • Can help manage comorbid psychiatric conditions [10]
  • Olanzapine may be considered in selected patients to assist with weight gain. [24]

The antidepressant bupropion lowers the seizure threshold and is contraindicated in individuals with a history of eating disorders because these individuals have an increased risk of dehydration and electrolyte imbalances, which can also cause seizures. [10]

Management of common complications

Sexually active patients with amenorrhea or irregular menses can still become pregnant; counsel patients appropriately on contraception. [18]

Differential diagnosestoggle arrow icon

The differential diagnoses listed here are not exhaustive.

Prognosistoggle arrow icon

Individuals with AN may switch from one subtype to another or develop a different eating disorder, such as bulimia nervosa. [7][13]

The high mortality rate in AN is due to associated medical complications (e.g., arrhythmia, bradycardia) and the high suicide rate in affected individuals. [15][25]

Special patient groupstoggle arrow icon

Anorexia nervosa in pregnant patients [27]

Pregnant patients with AN require multidisciplinary care involving their primary care doctor, obstetrician, psychiatrist, and dietitian. [29]

Referencestoggle arrow icon

  1. American Psychiatric Association. The American Psychiatric Association Practice Guideline for the Treatment of Patients with Eating Disorders. . 2022.doi: 10.1176/appi.books.9780890424865 . | Open in Read by QxMD
  2. Hornberger LL et al. Identification and Management of Eating Disorders in Children and Adolescents. Pediatrics. 2021; 147 (1).doi: 10.1542/peds.2020-040279 . | Open in Read by QxMD
  3. Klein DA, Sylvester JE, Schvey NA. Eating Disorders in Primary Care: Diagnosis and Management. Am Fam Physician. 2021; 103 (1): p.22-32.
  4. Guidebook for Nutrition Treatment of Eating Disorders. Updated: November 1, 2020. Accessed: August 4, 2022.
  5. Eating Disorders: A Guide to Medical Care. Updated: January 1, 2021. Accessed: July 20, 2022.
  6. Society for Adolescent Health and Medicine. Medical Management of Restrictive Eating Disorders in Adolescents and Young Adults. J Adolesc Health. 2022; 71 (5): p.648-654.doi: 10.1016/j.jadohealth.2022.08.006 . | Open in Read by QxMD
  7. Mitchell JE, Peterson CB. Anorexia Nervosa. N Engl J Med. 2020; 382 (14): p.1343-1351.doi: 10.1056/nejmcp1803175 . | Open in Read by QxMD
  8. Attia E, Steinglass JE, Walsh BT, et al. Olanzapine Versus Placebo in Adult Outpatients With Anorexia Nervosa: A Randomized Clinical Trial. Am J Psychiatry. 2019; 176 (6): p.449-456.doi: 10.1176/appi.ajp.2018.18101125 . | Open in Read by QxMD
  9. Gynecologic care for adolescents and young women with eating disorders. Updated: June 6, 2018. Accessed: January 29, 2022.
  10. Hudson JI, Hiripi E, Pope HG Jr, Kessler RC. The prevalence and correlates of eating disorders in the National Comorbidity Survey Replication.. Biol Psychiatry. 2007; 61 (3): p.348-58.doi: 10.1016/j.biopsych.2006.03.040 . | Open in Read by QxMD
  11. National Institute of Mental Health: Eating Disorders. Updated: November 1, 2017. Accessed: October 9, 2020.
  12. Udo T, Grilo CM. Prevalence and Correlates of DSM-5–Defined Eating Disorders in a Nationally Representative Sample of U.S. Adults. Biol Psychiatry. 2018; 84 (5): p.345-354.doi: 10.1016/j.biopsych.2018.03.014 . | Open in Read by QxMD
  13. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. American Psychiatric Association ; 2013
  14. Steinglass JE, Dalack M, Foerde K. The promise of neurobiological research in anorexia nervosa. Curr Opin Psychiatry. 2019; 32 (6): p.491-497.doi: 10.1097/yco.0000000000000540 . | Open in Read by QxMD
  15. Mazzeo SE, Bulik CM. Environmental and Genetic Risk Factors for Eating Disorders: What the Clinician Needs to Know. Child Adolesc Psychiatr Clin N Am. 2009; 18 (1): p.67-82.doi: 10.1016/j.chc.2008.07.003 . | Open in Read by QxMD
  16. Mountjoy M, Sundgot-Borgen J, Burke L, et al. The IOC consensus statement: beyond the Female Athlete Triad—Relative Energy Deficiency in Sport (RED-S). Br J Sports Med. 2014; 48 (7): p.491-497.doi: 10.1136/bjsports-2014-093502 . | Open in Read by QxMD
  17. Bakalar JL, Shank LM, Vannucci A, Radin RM, Tanofsky-Kraff M. Recent Advances in Developmental and Risk Factor Research on Eating Disorders. Curr Psychiatry Rep. 2015; 17 (6).doi: 10.1007/s11920-015-0585-x . | Open in Read by QxMD
  18. Mehler PS, Brown C. Anorexia nervosa – medical complications. J Eat Disord. 2015; 3 (1).doi: 10.1186/s40337-015-0040-8 . | Open in Read by QxMD
  19. Lechin F. Anorexia nervosa depends on adrenal sympathetic hyperactivity: opposite neuroautonomic profile of hyperinsulinism syndrome. Diabetes Metab Syndr Obes. 2010: p.311.doi: 10.2147/dmsott.s10744 . | Open in Read by QxMD
  20. Misra M, Klibanski A. Endocrine consequences of anorexia nervosa. Lancet Diabetes Endocrinol. 2014; 2 (7): p.581-592.doi: 10.1016/s2213-8587(13)70180-3 . | Open in Read by QxMD
  21. Harrington BC, Jimerson M, Haxton C, Jimerson DC. Initial evaluation, diagnosis, and treatment of anorexia nervosa and bulimia nervosa. Am Fam Physician. 2015; 91 (1): p.46-52.
  22. Engelhardt C, Föcker M, Bühren K, et al. Age dependency of body mass index distribution in childhood and adolescent inpatients with anorexia nervosa with a focus on DSM-5 and ICD-11 weight criteria and severity specifiers. Eur Child Adolesc Psychiatry. 2020; 30 (7): p.1081-1094.doi: 10.1007/s00787-020-01595-4 . | Open in Read by QxMD
  23. Lock J, La Via MC. Practice Parameter for the Assessment and Treatment of Children and Adolescents With Eating Disorders. Journal of the American Academy of Child & Adolescent Psychiatry. 2015; 54 (5): p.412-425.doi: 10.1016/j.jaac.2015.01.018 . | Open in Read by QxMD
  24. Westmoreland P, Krantz MJ, Mehler PS. Medical Complications of Anorexia Nervosa and Bulimia. Am J Med. 2016; 129 (1): p.30-37.doi: 10.1016/j.amjmed.2015.06.031 . | Open in Read by QxMD
  25. Arcelus J et al. Mortality rates in patients with anorexia nervosa and other eating disorders. A meta-analysis of 36 studies.. Arch Gen Psychiatry. 2011; 68 (7): p.724-31.doi: 10.1001/archgenpsychiatry.2011.74 . | Open in Read by QxMD
  26. $Contributor Disclosures - Anorexia nervosa. All of the relevant financial relationships listed for the following individuals have been mitigated: Alexandra Willis (copyeditor, was previously employed by OPEN Health Communications). None of the other individuals in control of the content for this article reported relevant financial relationships with ineligible companies. For details, please review our full conflict of interest (COI) policy.
  27. Pan JR, Li TY, Tucker D, Chen KY. Pregnancy outcomes in women with active anorexia nervosa: a systematic review. J Eat Disord. 2022; 10 (1).doi: 10.1186/s40337-022-00551-8 . | Open in Read by QxMD
  28. Lammi-Keefe CJ, Couch SC, Kirwan JP. Handbook of Nutrition and Pregnancy. Humana Press ; 2018
  29. Ward VB. Eating disorders in pregnancy. BMJ. 2008; 336 (7635): p.93-96.doi: 10.1136/ . | Open in Read by QxMD

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