Some of us might have a friend — or might be that friend — who’s always trying a new diet, cutting hangouts short to go to the gym, or critiquing parts of their body.

While these behaviors don’t necessarily signal a serious problem, an excessive focus on weight and food and poor body image can be warning signs of a little-known class of eating disorders: “Other Specified Feeding or Eating Disorder,” also known as OSFED.

Eating disorders are common in people of all ages, sexes, and races. According to the National Association of Anorexia Nervosa and Associated Disorders, at least 30 million people in the United States have one of these disorders.

Anorexia nervosa and binge eating disorder each affect 0.8 percent of Americans at some point in their lifetime, while bulimia affects about 0.3 percent.Udo T, et al. (2018). Prevalence and correlates of DSM-5-defined eating disorders in a nationally representative sample of U.S. adults. DOI: 10.1016/j.biopsych.2018.03.014

An estimated 30 percent of people who get treated for an eating disorder have OSFED. It can pose serious physical and mental health risks. In some cases, it can even be life threatening

Here, we explore this lesser-known category of eating disorders. We’ll look at what causes them and why changing disordered eating habits is both possible and important.

This information can mean the difference between struggling (or watching a friend struggle) with an unacknowledged illness and developing the awareness to create a healthier relationship with food.

OSFED used to be known as Eating Disorder Not Otherwise Specified (EDNOS). The term was a catchall for people who didn’t easily fit the diagnostic criteria for anorexia, bulimia, or binge eating disorder.

Because EDNOS was such a big bucket, most people with eating disorders fell into it. Then, in 2013, the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) refined EDNOS into the more specific diagnosis of OSFED.

The new classification points to the fact that eating disorders are not always black and white and that people can show disordered eating patterns even if they don’t qualify for a specific diagnosis. It also underscores how severe this disorder can be.

OSFED includes five subtypes:

  1. Atypical anorexia: features of anorexia, but the person is still within or above their “normal” weight range
  2. Bulimia nervosa: bulimic episodes that do not happen often and/or last long
  3. Binge eating disorder: binge episodes that do not happen often and or/last long
  4. Purging disorder: purging at least once a week, without bingeing
  5. Night eating syndrome: consuming a large number of calories after dinner or waking in the middle of the night to eat

OSFED can encompass a number of physical and emotional symptoms, including:

  • weight fluctuations (loss or gain)
  • rigid food rules and/or diets
  • excessive exercise or other behaviors to rid the body of food (purging, for example)
  • binge eating
  • negative body image
  • loss of menstrual periods
  • loss of sex drive
  • dizziness or fainting
  • depression
  • anxiety

“[OSFED] is not dieting to fit into a prom dress or running a 5K race with your friends. It’s when your relationship with food, shape, and weight is truly interfering with your life,” says Jennifer Thomas, Harvard Medical School psychology professor and co-director of the Eating Disorders Clinical and Research Program at Massachusetts General Hospital.

A person with OSFED might binge-eat on occasion or purge after eating a small amount of food, among other symptoms. Thomas also notes that fad diets may make eating disorders harder to detect.

“Lots of new health trends are just dieting in disguise… People are going gluten-free or vegetarian, or they’re going on a raw food diet or a juice fast,” she says. “Not everyone who has those behaviors has an eating disorder, but hiding disordered eating behind ‘healthy eating’ certainly can increase the time until someone is actually detected as a case.”

The causes of OSFED are a combination of genetic, environmental, social, and cultural factors.

Eating disorders run in families. People with a parent or sibling who has an eating disorder are much more likely to have one themselves. Twins, in particular, are at higher risk of both developing the disorder.Peterson CM, et al. (2016). Genetic and environmental components to self-induced vomiting. DOI: 10.1002/eat.22491

Researchers are looking at the role of epigenetics in the development of eating disorders. That’s the process by which environmental factors like diet or stress change the way genes are expressed. A 2019 study showed that behaviors like binge eating and purging can actually change a person’s epigenetic profile.Hubel C, et al. (2019). Epigenetics in eating disorders: A systematic review. DOI: 10.1038/s41380-018-0254-7

The environment itself plays a role in the development of eating disorders, OSFED included. Negative messages about body weight from family and friends can lead someone down the path toward one of these disorders.

Research shows that romantic partners can also have an influence on disordered eating habits, especially when they encourage their partner to diet (we’re looking at you, Peloton).Eisenberg ME, et al. (2013). Dieting and encouragement to diet by significant others: Associations with disordered eating in young adults. DOI: 10.4278/ajhp.120120-QUAN-57

Interactions with friends contribute too. College roommates’ dieting has been shown to predict scores on a test that analyzes disordered eating habits and the “drive for thinness.”Keel PK, et al. (2013.) Influence of college peers on disordered eating in women and men at 10-year follow-up. DOI: 10.1037/a0030081

Unhealthy body type images in media — especially social media — may also promote eating disorders, and at an early age.

In one 2019 study, seventh and eighth graders who had more Snapchat, Tumbler, Instagram, and other social media accounts were more likely to overestimate their weight and have disordered eating behaviors.Wilksch SM, et al. (2019). The relationship between social media use and disordered eating in young adolescents. DOI: 10.1002/eat.23198

The prevalence of OSFED suggests a society-wide issue when it comes to promoting and cultivating healthy body image and self-esteem.

The more we engage in “fat talk” (like “My arms are so flabby” or “I can’t believe how big my thighs look”), the more dissatisfied we feel about our bodies. And the more dissatisfaction and guilt we feel, the more we engage in fat talk.

Ultimately “the main feature that cuts across all eating disorders… is feeling like your shape and weight is one of the most important factors that determines how worthwhile you are as a person,” Thomas says.

A problematic relationship with food can make a person unhappy and negatively affect their mental health. It can also be physically dangerous and potentially life threatening.Heron KE, et al. (2014.) Eating behaviors and negative affect in college women’s everyday lives. DOI: 10.1002/eat.22292

OSFED and other eating disorders can damage just about every organ and system in your body. When left untreated, they can cause heart failure, intestinal blockage, nerve damage, bone loss, and other serious complications.

“The gray area between normal eating and [a full-blown disorder] is home to a great deal of pain and suffering,” Thomas says. “There are some studies that indicate that the mortality risk is just as high in people with [OSFED], versus full-syndrome anorexia.”

Treatment for OSFED is personalized based on the specific type a person has. In general, it’s important to get treated as early as possible by a team of professionals that includes a psychologist, a psychiatrist (if needed), a dietitian, and a medical doctor.

Treatment addresses both the physical and emotional symptoms of OSFED. Therapy can help eliminate the harmful thoughts that contribute to disrupted eating patterns. Medicine can improve the physical effects of the eating disorder.

Those who struggle with OSFED or any other eating disorder should know that a full recovery is possible. While people with OSFED may believe they are not sick enough to seek help, even those who haven’t reached an extreme weight can benefit from treatment.

OSFED may not be as well known as anorexia nervosa or bulimia, but it is just as serious — even potentially life threatening. It stems from the same types of genetic and environmental causes as other eating disorders.

Treatment requires a team approach, with strategies that address both the emotional and the behavioral sides of the condition. With prompt treatment, recovery from OSFED is possible.

Editor’s note: Interviews have been edited and condensed for clarity.