Diagnosis of eating disorders is a process that begins with acceptance of its presence. Often the patient needs to be convinced of its presence as there is severe denial and resistance to the problem.

There are too many patients that diagnose themselves as being allergic to gluten or carbohydrates and resort to restrictive diets. In addition, when diagnosed in children, parents often perceive it as a parental failure and there are multiple factors that influence the detection of eating disorders.

Diagnosis involves:

Interview based tests

Medical interviews with a supportive companion (preferred) are the initial steps in diagnosis. The physician tries to find out additional information on the patient's eating history. The interviews use various questionnaires to assess the patients.

The Eating Disorders Examination (EDE), which is an interview of the patient by the doctor, and the self-reported Eating Disorders Examination-Questionnaire (EDE-Q) are both considered valid tests.

Another test is called the SCOFF questionnaire, which can help identify both very young and adult patients who meet the full criteria for anorexia or bulimia nervosa.

Screening questionnaire

A screening questionnaire is first applied:

• How many diets have you been on in the past year?
• Do you think you should be dieting?
• Are you dissatisfied with your body size?
• Does your weight affect the way you think about yourself?

A positive response to any of these questions warrants further evaluation

SCOFF questionnaire

Broadly the SCOFF Questionnaire includes questions like:

• Do you make yourself sick because you feel uncomfortably full?
• Do you worry you have lost control over how much you eat?
• Have you recently lost more than one stone's worth of weight (14 pounds or 6.4kg) in a 3-month period?
• Do you believe yourself to be Fat when others say you are too thin?
• Would you say that food dominates your life?

One point for every yes answer; a score 2 indicates a likely case of anorexia nervosa or bulimia nervosa

Bulimia diagnosis

For bulimia diagnosis there has to be at least two bulimic episodes per week for 3 months. Since there may be dental and gum related problems in bulimic patients dentists and oral pathologists may also help in diagnosis.

Anorexia nervosa diagnosis

For diagnosis of anorexia nervosa the criteria are patients refusal to maintain a body weight normal for age and height and an intense and irrational fear of becoming fat even though underweight. Patients typically have a distorted self-image that results in diminished self-confidence and do not accept that fact that they may be seriously emaciated and ill.

There is in addition loss of menstrual function for at least 3 months. Once detected, anorexia may be categorized further. Some have restrictive anorexia nervosa who practice severe dieting only while other may have Anorexia bulimia who have binge-purge behaviour.

Medical tests for complications

Medical tests are advised to detect and rule out complications of eating disorders. Tests should include:

Differential Diagnosis

Other disorders that mimic eating disorders include:

• Hyperthyroidism – overactive thyroid
• Cancers
• Inflammatory bowel disease like Crohn’s disease and ulcerative colitis
• Immunodeficiency and AIDS like states
• Chronic infections
• Malabsorption syndromes
• Addison's disease
• Diabetes

Co-existing diseases

Some diseases commonly co-exist among patients with eating disorders. These include:

• Depression - Major depression is the most common comorbid condition among patients with anorexia
• Anxiety disorders - Anxiety disorders, especially social phobia, also are common
• Obsessive-compulsive disorder – This has a prevalence of 30 percent among patients with eating disorders
• Substance abuse – This has prevalence is estimated at 12 to 18 percent in patients with anorexia and 30 to 70 percent in patients with bulimia
• Schizophrenia