What Is Atypical Anorexia Nervosa?

When we think of someone with anorexia nervosa, we picture a teenager or young adult who is underweight, often dramatically so. The patient, usually a girl, is driven by an obsessive fear of being fat, even though she’s far from it, and has been dieting and exercising excessively to lose weight.

There is another kind of anorexia that’s called atypical anorexia nervosa. In this case the teenager, almost always a girl, is not noticeably thin. Usually overweight to begin, she too has become obsessed with extreme dieting and exercise, and has lost a dramatic amount of weight. She has the same thoughts and behaviors as someone with typical anorexia and is putting similar stress on her body. But she doesn’t look unhealthy, which means that this disorder often goes unnoticed.

To explain atypical anorexia, Daniel Le Grange, PhD, director of the Eating Disorders Program at the University of California, San Francisco, uses the example of two hypothetical 14-year-old girls. Both are about five foot two inches tall. One used to weigh about 115 pounds, but when she is referred for treatment, she weighs 85 pounds. Over the past 12 months, she’s been starving herself and exercising aggressively because she believes she’s fat. She’s stopped menstruating and is in a medical crisis. That’s typical anorexia.

The other 14-year-old had previously weighed 175 pounds. Then, in about 6 months, she’s lost more than 50 pounds.  When she is referred for treatment she weighs 120 pounds — a normal, seemingly healthy weight for her age and height. But because of the magnitude and speed of weight loss, she’s also stopped menstruating and is medically unstable, which means her vital signs are dangerously low. This is atypical anorexia.

“The first young person looks emaciated, sick and terribly unwell,” Dr. Le Grange explains. “Visually, the second young person, if you apply western ideals — and I apologize for these gendered and western stereotypes — looks just fine. But by her own historical growth and weight trajectory, she’s way underweight.” The bottom line is that a “healthy” weight is actually unhealthy for this person, because of her weight history and the speed with which the weight was lost.

Atypical anorexia is dangerous because it’s often not recognized — families and even doctors might be praising a young woman for impressive weight loss when she is actually critically unwell.

Atypical anorexia patients have all the same symptoms and behaviors as typical patients except the most visible one: low weight. A 2016 study found that they were just as physically compromised and as distressed emotionally as their typical counterparts.

Both are driven by obsessive fear of weight gain and being fat. But atypical anorexia patients had what the study called “significantly higher levels of distress related to eating and body image” and “a fear of fatness that their weight history might exacerbate.”

Atypical patients also have low self-esteem and almost half report self-harm and suicidal ideation. They are just as likely as other anorexia patients to withdraw socially, and to have related mental health issues, most often depression or anxiety.

In the case of typical anorexia, the first priority is obviously for the girl to restore weight to stabilize her body. The girl with atypical anorexia also needs to regain weight to stabilize her vital signs and begin having her period again. But that would mean moving from what would normally be a healthy weight to one that’s usually considered overweight. That poses a difficult dilemma for the girl, her family and the doctor who’s treating her.

To get her period again, Dr. Le Grange explains, she would probably have to reach at least the weight she was when she stopped having it on the way down. That means that the young woman who started at 175 pounds and lost her menstrual cycle at around 155 may very well have to return to 155 or 160 in order to get healthy. And that makes recovery especially difficult.

“You’re telling a 15-year-old that she needs to regain most of the weight she’s lost,” he notes. “And more than likely she’ll reply, ‘But I’ll be fat and my peers will tease me.’ The parents feel uncomfortable, and the patient gets more and more distressed, and you are pushing someone’s weight back up into the overweight range. Many experts in our field will agree that we have to embark on this ‘weight restoration’ journey with the utmost of caution.”

Once a patient has stopped weight loss and has stabilized medically, a clinician would encourage her to work towards weight gain at a much slower pace than one would with a typical anorexia patient, he explains. The goal would be to stop as soon as menstruation is restored.

Atypical anorexia nervosa is a relatively new diagnosis. It was officially codified as a type of anorexia in DSM-5, which was published in 2013. But clinicians have been studying patients who fit this description for more than a decade. Dr. Le Grange cites an eating disorders service at the Royal Children’s Hospital in Melbourne, Australia as leaders in describing this disorder.

And that hospital has seen a growing percentage of anorexia patients who are the atypical type. “Back in 2007 or 2008, about 20 percent of the patient population at that eating disorder service presented with atypical anorexia nervosa,” Dr. Le Grange reports. “In 2021, a good 40 percent of the referrals to that service would meet criteria for atypical anorexia nervosa”.

Dr. Le Grange adds that the percentage is similar in the eating disorders program he runs in San Francisco: “Here at UCSF at least a third of our patients present with atypical anorexia nervosa.”

One way to gauge the seriousness of atypical anorexia is to look at the rate at which patients are referred for hospitalization. To this end, Dr. Le Grange is involved in a UCSF study run by Andrea Garber, PhD, chief nutritionist, comparing typical vs atypical patients in inpatient treatment. While the study is still ongoing, he reports, it appears that atypical cases are just as likely to require inpatient treatment for medical stabilization.

That may seem surprising, because these kids might weigh 130 pounds. “But it’s where they come from and how quickly they’ve lost their weight that makes them present in equal numbers to the inpatient service based on medical instability,” Dr. Le Grange notes.

Medical instability is defined by a group of vital signs that indicate that the body is severely stressed. They include malnutrition, dehydration, and abnormally low heart rate, blood pressure and body temperature. Patients with atypical anorexia present with just as many dangerously low vital signs as their typical counterparts, Dr. Le Grange notes.

In addition, prolonged malnutrition during the teenage years can have long-term consequences.

Infertility is one cause of concern. While many teenagers and young women with anorexia say they don’t care about losing menstruation — or are actually relieved by its disappearance — it can lead to permanent fertility challenges later in life when they may feel very differently about having a family of their own.

Prolonged malnutrition can also lead to stunted growth. The early teen years are when there is normally a growth spurt, which ends at around 16, reports Dr. Le Grange. “If you miss the window for that optimal growth spurt, even if you have become weight restored, you can never recover the height.”

And bone health is another thing that’s endangered by anorexia. Teenagers who are nutritionally compromised are not developing optimal bone density. “Depending on the timing of starvation, they lose the capacity to have optimal bone health even if they recover at age 18,” Dr. Le Grange explains.  “So they go into adulthood with compromised bone health.” He adds that young people with anorexia may even have osteoporosis or osteopenia at age 17.

The most difficult thing for atypical anorexia patients and their families to understand is why a body that’s at a supposedly healthy weight needs to regain weight in order to become actually healthy. An atypical patient might have stabilized vital signs after regaining 4 or 5 pounds, he explains. But the body won’t restart menstruation until the patient gets back at least to the point where it stopped.

Why? Dr. Le Grange says the menstrual cycle is triggered, among other factors, by a certain body fat percentage. “Each female’s body fat percentage is biologically determined. So, some women require body fat percentages up above 20 to have regular cycles.” In atypical anorexia, he notes, “It’s often the case that one or both parents are somewhat overweight and have been so historically. Some of their siblings might also be on the heavy side, too. All in keeping with their family make-up”.

A patient with atypical anorexia who tries to maintain the lower weight with a healthy diet is often fighting her own genetic make-up, body composition, and personal weight history, he explains. With any increase in nutrition, the body will put weight back on. “Your body is trying to pull you back to the higher weight,” as Dr. Le Grange puts it.

Recognition of atypical anorexia means a fundamental shift in our broader understanding of anorexia nervosa and what a clinician diagnosing someone with disordered eating is looking for.

Part of our understanding of anorexia nervosa patients has been that the disorder is triggered by a distorted self-image, in which a young person perceives herself to be overweight when she isn’t. But for a sizeable number of patients who’ve become obsessed with their weight and shape — the atypical patients — the prospect of appearing overweight is not an irrational fear or fantasy.

In the same vein, appearing underweight is no longer a reliable test of whether someone has anorexia. In an atypical patient, the body weight may not be too low by common standards, but the effects of malnutrition can be just as dangerous. These patients may be overlooked because they don’t fit the physical stereotype, even though they have the behavioral symptoms, which significantly disrupt their lives.

Given how common atypical anorexia is becoming, clinicians now need to look beyond body weight in recognizing anorexia, Dr. Le Grange concludes, “to entertain the idea of looking at someone who’s 80 pounds and someone who’s 130 pounds, and both of them can have anorexia nervosa.”