Eating Disorders: Anorexia Nervosa & Bulimia

Eating Disorders are a collection of psychiatric conditions that involve abnormal eating habits associated with physical and/or psychological problems. There are many causes of abnormal eating habits, but if the situation is better explained by another medical problem it is not classified as an eating disorder. For example, a depressed patient who loses their appetite has an abnormal level of food intake, but does not have an eating disorder. Our discussion will focus on Anorexia Nervosa and Bulimia Nervosa which have many similarities. In both cases patients are preoccupied with food, their physical appearance and how much they weigh. They may have low self-esteem due to their distorted self-image. These disorders are significantly more common in young females. The treatment for both disorders primarily focuses on SSRI antidepressants and various types of therapy.


There is a significant amount of overlap between the presentation of Bulimia and Anorexia Nervosa. The key distinguishing factor is the patient’s body mass index (BMI), which is very low in Anorexia Nervosa and normal to mildly elevated in Bulimia Nervosa. Despite popular belief, you cannot use the presence of purging activities alone to distinguish the 2 disorders. Patients with AN can use things like laxatives and intentional vomiting just like Bulimia.


Bulimia Nervosa = Periods of overeating (AKA binging) followed by compensatory activities (AKA purging) such as intentional vomiting, excessive exercising or inappropriate laxatives use. Patients feel as if they lose control during periods of binge eating. BMI is within normal ranges or slightly high (>20). Those that vomit may have alkalosis (due to loss of stomach acid), enlarged parotid glands, losses of enamel on teeth, or esophageal pathology. Those that use laxatives frequently may have acidosis due to the loss of bicarb. Although this warning is debated by some, current guidelines suggest not using Bupropion (antidepressant) in Bulimic patients as they may have an increased risk for seizures as a side effect.


Binge Eating Disorder was recently added the DSM so it is unlikely to show up on Step 1. It has similar binging behavior to Bulimia, but there is no purging and the patients don’t necessarily have body image issues.


Anorexia Nervosa = eating very little and/or purging as a result of a distorted body image. These patients may feel like they are overweight even if they are very thin. They have low BMIs (<17) and significant weight loss. Severe cases require hospitalization to correct starvation and the metabolic consequences.  When a female’s body fat percentage gets very low the pulsatile release of GnRH from the hypothalamus stops and causes Amenorrhea. It’s like the endocrine system is saying “I can’t have a baby right now. I’m not even getting enough food for just me right now.” Chronic Anorexia Nervosa can lead to osteoporosis due to the low levels of estrogen. Can look similar to hypothyroidism with fatigue and changes to skin/hair, but the key difference is hypothyroidism has weight gain.


* The term anorexia is used often in Step 1 to describe weight loss and a lack of appetite, but that is different than anorexia nervosa which is sometimes abbreviated as anorexia. Anorexia can be used to explain a symptom of any disease/illness or a side effect of a treatment. It is not psychological in origin. In fact patients with Anorexia Nervosa do not have Anorexia, because they usually still have an appetite and feel hungry. The presence of an appetite can be used to differentiate Anorexia Nervosa from things like depression.


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