Eating Disorders: Diagnosis

Text below adapted from The patient who has an eating disorder, Psychiatry in primary care, by David S. Goldbloom,  (CAMH, 2019). 

Weight history 

Take a comprehensive lifetime weight history that includes:

• current weight and height—Ask: “How do you feel about this weight?  At what weight do you feel fat?” 
• highest and lowest adult weights. 

Ask questions about the following issues to help clarify treatment goals and obstacles: 

• ideal weight—Ask: “How would your life be different at that weight?”
• menstrual threshold weight—target weight for treatment must be above this weight. 
• frequency and routine of weighing self—this information will help you understand how the eating disorder governs the patient’s life. 

Body image 

Ask the patient: 

• “How do you see yourself currently? Where exactly do you feel fat?” ·· “How much does your weight and shape determine how you feel about yourself  as a person?” 
• “Do you fear gaining even small amounts of weight?” 

Eating behaviours 

Ask the patient about: 

• dieting history 
• caloric and food group restrictions 
• episodes of binge eating with a sense of loss of control, and consumption of foods the patient typically would avoid. 

Purging behaviours 

Ask the patient about: 

• self-induced vomiting 
• use of laxatives, diuretics, diet pills 
• intensive exercise to lose weight 
• cigarette smoking to suppress appetite.

Medical Complications 

See Symptoms in Screening and Assessment. 

Psychiatric Complications 

Determine whether other psychiatric complications exist, including:

• depression 
• anxiety 
• obsessionality 
• impulsivity 
• substance use problems. 

Remember that depressed mood, anxiety and obsessional preoccupation with food, shape and weight are often integral aspects of an eating disorder,  rather than evidence of multiple concurrent diagnoses. 

Differential Diagnosis

Because you are a primary care practitioner, not an eating disorders specialist, you have the responsibility to rule out other causes of the clinical presentation. Although people can lose weight for many reasons, the diagnosis of an eating disorder requires the “nervosa” component—undue preoccupation with body weight and shape, its influence on self-perception and the morbid fear of becoming fat.

Other Physical Conditions

The medical differential diagnosis includes:

• hyperthyroidism
• malignancy
• malabsorption
• inflammation (e.g., Crohn’s disease, ulcerative colitis).

A careful history will rule out most of these possibilities, but a physical examination and some laboratory investigation will also help to clarify the diagnosis and demonstrate your concern for the comprehensive health of your patient.

Other Psychiatric Disorders or Problems

Other psychiatric disorders or problems that can be mistaken for an eating disorder include:

• depression (accompanied by a true anorexia and weight loss) ·· conversion disorder (belief that something is stuck in the throat and food cannot pass)
• schizophrenia (food avoidance based on the delusion that it is poisoned) ·· substance use (psychostimulants that induce weight loss).

Again, a careful and sympathetic history will usually clarify the diagnosis. Furthermore, your willingness to accept that the patient has an eating disorder will have a permissive effect on disclosure, since the patient has likely already made a diagnosis via the internet.

In Eating Disorders:

• Introduction
• The Primary Care Practitioner Role
• Screening & Assessment
• Diagnosis
• Treatment
  • Psychotherapy
  • Pharmacotherapy
• Resources & References