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Diagnosis of Eating Disorders

Eating Disorders, including Anorexia Nervosa, Bulimia Nervosa and Binge-Eating Disorder, are diagnosed based on a clinical assessment performed by a mental health professional, usually a psychologist or psychiatrist.  This assessment includes an interview with the patient and a review of any previous assessments in their medical records, and can also include an interview with the patient's family members or close friends.  The goal of this assessment is to determine whether the patient meets the clinical criteria for any of these conditions based on the reports that they or their family members and friends provide. 

Measuring the individual's weight and height are key features of these assessments. The Body Mass Index (BMI) is a standard way of quantifying a person's weight relative to their height, and is calculated by dividing one's weight in kilograms by the square of one's height in meters (kg/m2). The healthy range of BMI is considered to be between 18.5-25 kg/m2. Individuals with BMIs above 25 are considered to be overweight, and those below 18.5 to be underweight.

To be diagnosed with Anorexia Nervosa, one's weight must be less than 85% of the normal expected weight. This corresponds roughly to a BMI that falls below the 3rd percentile, and can be determined by using a BMI chart that plots the normal ranges of BMI based on a person's age. There exists a BMI chart for males and for females. The bottom thick curve with the numeral 3 in these charts is the line for the 3rd percentile; in Anorexia Nervosa, an individual's BMI would fall below this line. In adults, this corresponds to a BMI below 17.5.

Laboratory tests are important in order to determine whether there are any medical problems that have resulted from excessive weight loss or from binge-eating or purging behaviors.

Excessive weight loss can lead to physiological changes characteristic of starvation. These include:

  • Leukopenia and mild anemia
  • Elevated blood urea nitrogen (BUN) due to dehydration
  • Hypercholesterolemia
  • Abnormally elevated liver enzymes and serum amylase
  • Electrolyte abnormalities including hypocalcemia, hypomagnesemia, hypophosphatemia and hypozincemia
  • Low TSH accompanied by low serum thyroid hormone levels
  • Low serum estrogen in females and low serum testosterone in men
  • Abnormal heart rhythms, such as bradycardia and arrhythmias
  • Electroencephalographic (EEG) abnormalities and an increase in the ventricular-brain ratio as seen in brain imaging can occur is severe cases
  • Osteopenia and osteoporosis
  • Stunted growth and sexual development in children and adolescents
  • Lanugo hair, which is a fine fuzz that grows all over the body to compensate for low body fat

Excessive vomiting can result in:

  • Metabolic alkalosis (elevated serum bicarbonate)
  • Hypochloremia, hypokalemia and hyponatremia
  • Elevated serum amylase
  • Enlarged salivary glands
  • Tooth decay
  • Scarring on the knuckles or back of the hand, called Russell's sign, due to repeatedly using one's fingers to induce vomiting

Excessive laxative use can result in:

  • Metabolic acidosis
  • Electrolyte abnormalities including hypochloremia, hypokalemia and hyponatremia
  • Occult blood in the stool

There are certain rating scales that can help clinicians detect individuals who suffer from Eating Disorders and also quantify the levels of their symptoms.

The SCOFF questionnaire is a quick and easy screening tool, with only five short questions, that can help to identify individuals with Eating Disorders. Responding 'yes' to two questions or more suggests that one may have Anorexia Nervosa or Bulimia Nervosa.

The Eating Attitudes Test (EAT-26) is a self-rated scale that measures behaviors and attitudes characteristic of Anorexia Nervosa [ref].


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