What are atypical eating disorders?

What are atypical eating disorders?

"Atypical eating disorder" is not currently in the Diagnostic and Statistical Manual for Mental Disorders (DSM), the official list of all medically-recognized mental health conditions. But the term is frequently used to describe “other specified feeding or eating disorders” (OSFED), which is in the DSM.

The phrase is essentially used as a catch-all, to cover conditions that do not otherwise neatly fit into the established criteria of AN, BN, or BED. A person with an atypical eating disorder may show signs and symptoms of more classically understood eating disorders, such as binging, purging, restricting, or compulsively exercising, but these behaviors will present “atypically” due to their frequency, intensity, or severity.

Though they are classified as “other,” these conditions are still eating disorders, and can impact a person’s mental, physical, and social health in similar ways. People struggling with these conditions may experience difficulty maintaining responsibilities at home, work, or school, and the disordered eating behavior involved can be just as debilitating as typical eating disorders if left untreated. 

Many situations and types of symptoms can qualify as an atypical eating disorder. Two of the most noteworthy are called atypical anorexia nervosa (AAN) and atypical bulimia nervosa.^1,2

Atypical anorexia nervosa

Many traits of an atypical anorexia nervosa diagnosis mirror the same issues that drive AN, including: 

• A distorted perception of one's body shape, size, or weight 
• An intense fear of gaining weight
• Severe dietary restrictions

But there is one major difference between atypical anorexia symptoms and those of anorexia nervosa. With AAN, the condition is not associated with significant weight loss or being underweight. Indeed, people with AAN often maintain a weight that is within or above the expected range.

This can become a complicating factor when it comes to detection or treatment. It may be easier for someone within a "normal" weight range to hide their disordered patterns or behaviors, and the person themself may be able to more easily deny there's an issue, since they don't match the typical look of someone with anorexia nervosa.

Atypical bulimia nervosa 

Atypical bulimia nervosa (ABN) is used to describe a situation when someone may struggle with many aspects of bulimia nervosa, but not meet the full criteria for the condition. This could look like symptoms that do not occur as frequently, or do not happen as consistently or over a long enough period of time to receive a full BN diagnosis.

To meet the criteria for a typical BN diagnosis, someone will experience binging or purging behaviors at least once per week, over the course of three months.⁴ But if these behaviors occur less than once per week, or if the pattern has been present for less than three months, it can be considered ABN.

For these reasons, atypical bulimia nervosa is sometimes also known as bulimia nervosa of low frequency and/or limited duration.⁶

Are atypical eating disorders actually “atypical”?

Eating disorders are largely unique and individualized experiences, so thinking about them as “typical” or "atypical" at all may be perpetuating a false dichotomy. And OSFED is also a commonly diagnosed condition, which means that these "atypical" experiences are actually more common than their name may suggest. 

In fact, there were so many cases of these atypical behaviors being reported that in 2013, the American Psychiatric Association (APA) adjusted the classification of eating disorders, adding the diagnosis of atypical anorexia nervosa and bulimia nervosa of low frequency and/or limited duration. Before 2013, these conditions would have been called an eating disorder not otherwise specified (EDNOS).¹

Studies have demonstrated that these changes were appropriate, as up to 45% of people attending inpatient treatment for AN reported being at or above their expected weight. And this shift appears to be a new evolution of the condition, with treatment centers reporting a 600% increase in recent years in people receiving treatment for AN who are not “underweight."¹

These findings could indicate that AAN is a different condition, or it could show that current views of AN need to be updated to better reflect changes among those with disordered eating. Bulimia nervosa (of low frequency and/or limited duration) has received less attention, but like AAN, atypical bulimia might show that current definitions of BN may be outdated.

Is there risk with classifying eating disorders as “atypical”? 

Any disordered eating carries potential health risks, and this can be amplified by identifying a certain set of symptoms as “atypical." This kind of mindset, in both physicians and people struggling with these disorders, could lead to more people going undiagnosed. And, unfortunately, the longer these behaviors continue, the more harm they generally tend to cause.

From a clinical standpoint, someone who reaches some—but not all—of the criteria for an AN, BN, or BED diagnosis may not qualify for treatment. That's why some in the scientific community are calling for future assessments that focus more on the health and nutrition of the individual, rather than a number on the scale or frequency of unhealthy behaviors.³

There is also hope that by expanding the definition of what constitutes an eating disorder, more people who are struggling with their body image and eating behaviors will get the help they need. 

Treating atypical eating disorders

Although they are not considered "typical," these versions of eating disorders can still result in a number of unwanted physical and mental health effects. But the good news is, many of the same treatments that have shown success for AN, BN, and BED can be effective for treating atypical disorders as well.⁴

A few of the most helpful treatments for atypical eating disorders include:⁴

• Cognitive behavioral therapy (CBT) and CBT-E: CBT is a foundational eating disorder treatment, which helps shift a person’s thoughts, feelings, and behaviors towards more desirable outcomes. CBT-E is an enhanced form of the treatment, which has been adapted to treat a number of mental health conditions.
• Family-based treatments (FBT): This type of therapy engages all members of the family, incorporating them in someone's recovery journey and working to help shift the dynamics that factor into disordered eating behaviors.