Anorexia Nervosa: Inside One of the Most Prevalent Eating Disorders

Causes behind rising prevalence

Anorexia Nervosa (AN) is one of the most prevalent eating disorders (EDs). It has been estimated that the prevalence for females diagnosed with AN is up to 4%, whereas for males up to 0.3%. The overall prevalence of AN has been stable for decades, however there has been a slight increase in the number of diagnoses of AN in young adolescents (less than 15 years of age). It is important to note that the prevalence of EDs is often underestimated, given that seeking help, especially in the case of AN, is avoided due to denial, shame, or stigma.

It has been suggested that the increase in numbers of young individuals suffering from AN is not necessarily the outcome of more individuals affected by it, instead, by the increase in the number of people seeking help. Speculatively, this largely is due to efforts made to tackle stigma among EDs in general, raising public awareness and broadening the diagnostics of EDs.

Criteria for diagnosis

Even though AN is a neuropsychological disorder, for a conclusive diagnosis, your primary care physician is likely to perform a physical examination and lab tests in addition to a psychological evaluation performed by a psychologist.

There is a combination of required features to be met for an individual to be diagnosed with AN. As mentioned before, in addition to physical examination, several behavioral and psychological features as defined by International Classification of Diseases (ICD-11), World Health Organization, must be met:

  • Body mass index (BMI) less than 18.5 kg/m2 (adults) and BMI-for-age under 5th percentile for children and adolescents.
  • Rapid weight loss (e.g., more than 20 % of total body weight within 6 months) may replace the low body weight guideline as long as other diagnostic requirements are met.
  • A persistent pattern of restrictive eating or other behaviors that are aimed at establishing or maintaining abnormally low body weight. For example fasting, choosing low-calorie food, excessively slow eating of small amounts of food, hiding or spitting out food (reducing energy intake) or excessive exercise, deliberated exposure to cold (increase energy exposure).
  • Low body weight is overvalued and central to the person's self-evaluation, or the person's body weight or shape is inaccurately perceived to be normal or even excessive. May be manifested by behaviors such as repeatedly checking body weight using scales, tape measures, or reflection in mirrors. Constant monitoring of the calorie content of food. Extreme avoidant behaviors, refusal to have mirrors at home, avoidance of tight-fitting clothes, or refusal to know one`s weight or purchase clothing with specified sizing.

The International Classification of Diseases (ICD-11) has been used as the official reporting system by member states from January 1, 2022.


Based on the different symptomology there are 4 subgroups of AN diagnosis:

  1. Restricting type, exhibited primarily by severe limitation of food intake as the primary means to weight loss.
  2. Binge eating/purging type, in addition to restrictive food intake, there are periods of food intake that are compensated by self-induced vomiting, laxative or diuretic abuse, and/or excessive exercise.
  3. Atypical Anorexia Nervosa, the restrictive behaviors of food intake and fear of weight gain are present, however the individual does not meet the low weight criteria seen in typical AN.
  4. Other Specified feeding or eating disorders (OSFED), a recent addition to the diagnostic manuals for AN and Bulimia Nervosa (BN). This diagnostic category was developed to encompass those individuals who do not meet strict diagnostic criteria for AN or BN, however, are recognized as suffering from a significant eating disorder.

Currently, the Transdiagnostic view of eating disorders has been a dominant perspective on eating disorders, which recognizes that mechanisms and behaviors involved in EDs are largely similar. In addition, migration between different EDs commonly occurs after the remission of AN. Longitudinal studies indicate that the majority of individuals diagnosed with a particular type of AN over the years crossover, i.e. are re-diagnosed at reassessment with another type of AN or BN.

Effects of AN

The restricting, purging and excessive compensatory behaviors in AN have a significant impact on physical and psychological health. The reports suggest that suffering from AN increases mortality by up to 5 times. It has been suggested that above 50% of deaths resulting from AN can be attributed to medical consequences that manifest throughout the course of the disorder. These can be broadly categorized as follows:

  • Brain and nerves: memory performance, changes in brain chemistry, and mood swings (irritability, low mood) can induce fainting, trouble concentrating, consumed with thoughts of food intake/restriction, fear, and anxiety of gaining weight.
  • Hair: thin and brittle hair, loss of hair.
  • Heart: low blood pressure, slowed heart rate, heart failure and palpitations (feeling of heart pounding, racing).
  • Blood: anemia.
  • Skin: higher exposure to bruising, brittle nails, fine hair growth on the entire body, yellowish skin.
  • Kidneys: kidney failure, proneness to kidney stones.
  • Muscles, joints, and bones: swollen joints, osteoporosis (weakened, fracturing bones), weak muscles.
  • Intestines: constipation, bloating.
  • Hormones: loss of menstrual cycle (in women), disrupted development (in young adolescents), fertility issues.
  • Body fluids: low levels of potassium, magnesium, and sodium (essential for healthy brain functioning).

Predisposing, triggering, and maintenance factors

To date, it is unclear what causes AN, however, the contemporary literature suggests several factors that are associated with an increased risk of being diagnosed with AN:

  • Genetic contribution.
  • Personality traits such as negative self-image and perfectionism.
  • Trauma.
  • Physical and/or sexual abuse.
  • Cultural pressure (e.g. idolizing thin body imagery).

Regardless of the factors that may increase the risk of the diagnosis, it has been proposed that a single or combination of factors may trigger the onset of AN:

  • Loss and/or conflict.
  • Bullying (especially comments about weight).
  • Being overweight as a child (leads to increased self-awareness of food intake, encourages a distorted perception of one's own body image).
  • Early puberty.
  • High performance pressure (either from family, school, university, work, colleagues).
  • Changes in living situation (e.g. abrupt, forced, or sudden relocation).
  • Extensive dieting.

The most common age for diagnosing AN is between 15 and 30 years of age, whereas diagnosis made after 30 years of age is quite rare.

The persisting maintenance of the unhealthy restrictive, purging, and compensatory behaviors has been shown to be in part caused by:

  • Family conflict, especially those triggered by eating disorders.
  • Negative environmental reactions.
  • Psychological symptoms (coexisting mental disorders or disrupted function as a result of malnutrition), positive symptoms (sense of control, inner unrest resolution, avoidance of negative feelings).

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