August/September 2021 Issue

Atypical Anorexia Nervosa
By Hadley Turner
Today’s Dietitian
Vol. 23, No. 7, P. 42

This eating disorder requires nutrition professionals to think differently about a familiar diagnosis.

When Marie, a woman in her 50s with atypical anorexia nervosa (AN), presented for inpatient eating disorder treatment, she was consuming only 400 kcal per day and suffering from kidney injury. But she was in a larger body. And within her first hour of treatment, the inpatient dietitian at the clinic told her she “didn’t look like” she had an eating disorder and that she “could reasonably lose another 10 lbs.”1

This encounter can be difficult for many RDs to imagine, but Marie isn’t alone. Her experience is one of numerous incidents recorded by Erin Harrop, PhD, LICSW, an assistant professor in the Graduate School of Social Work at the University of Denver in Colorado, whose research will be discussed later in this article.

Atypical AN is so termed because while patients exhibit traditional AN symptoms such as distorted body image, hyperfocus on weight and body shape, and severe calorie restriction, their weight doesn’t meet the weight criterion for AN (a BMI lower than 18.5 kg/m2 for adults and a weight in the fifth percentile for age for children).2 Those with atypical AN don’t present as emaciated but instead are “normal weight” or higher weight, some having a BMI that would be categorized as “overweight” or “obese.”

When it comes to eating disorder screening and treatment, Harrop and other researchers and practitioners have found that patients with atypical AN often fall through the cracks. Patients in larger or “normal-weight” bodies don’t tend to be screened for eating disorders and sometimes are turned away when they seek care for their condition.

While the story of atypical AN isn’t explicitly the story of weight bias, understanding and countering weight bias is crucial to diagnosing and treating patients in a timely manner. Challenging the narrative of what severe calorie restriction looks like—in their own minds, among their colleagues, and in the field—provides RDs with a golden opportunity to prevent the deleterious effects of untreated AN and atypical AN, and ultimately save lives.

Despite its name, atypical AN is far from atypical. In a community study of young women, lifetime prevalence by age 20 was 2.8% for atypical AN compared with 0.8% for AN.3 But these percentages likely would have been higher had men been included in the study. According to Andrea Garber, PhD, RD, a professor of pediatrics at the University of California, San Francisco, young men with restrictive behaviors tend to meet the atypical AN weight criterion because of their greater muscle mass.

The condition’s prevalence could increase with age, too. A study published in April 2021 of 1,137 US military veterans who served in Iraq and/or Afghanistan found that 13.6% of women and 4.9% of men met criteria for probable atypical AN.4

Diagnosis and Symptoms
In terms of diagnostic criteria as outlined in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5), atypical AN is nearly identical to AN—except for BMI/weight status.

The other diagnostic criteria include the following2:

• restricted calorie intake relative to requirements, leading to a significantly low body weight (as mentioned in the previous paragraph) for age, sex, development, and physical health;
• “intense fear” of weight gain or becoming fat, and continuous behavior to prevent weight gain; and
• distorted sense of one’s body, self-worth tied to body weight or shape, and lack of recognition about the severity of low body weight (when body weight is indeed low).

Despite the similarities between atypical AN and AN, atypical AN is listed in the DSM-5 under the category other specified feeding and eating disorders (OSFED)—previously known as eating disorder, not otherwise specified—which includes disordered eating behaviors that don’t meet the criteria for a specific eating disorder.2

Research has suggested some small distinctions between AN and atypical AN. A 2016 Australian study that compared symptoms of adolescents with AN vs those with atypical AN found no significant difference between the groups for symptoms such as suicidal ideation, bradycardia, and orthostatic instability, and behaviors such as laxative use and compulsive exercise. But participants with atypical AN scored significantly higher than their counterparts with AN on weight, shape, and eating concerns (based on the gold-standard Eating Disorders Examination), suggesting those with atypical AN experience significantly greater distress. According to the authors, this may be due to greater disparity between their current weight and perceived ideal weight.5 That said, AN hasn’t been found to be more common in higher-weight individuals, at least in adolescence.6

It’s critical to keep in mind something RDs might find paradoxical: Despite severe calorie restriction, some individuals with atypical AN will maintain and even gain weight. But how can this be?

The answer is two-fold. First, even without calorie restriction, genetic differences are linked to different weight gain and maintenance responses to similar environmental circumstances; some individuals, for example, have a genetic predisposition to maintain a high weight, which historically has been an evolutionary advantage due to the survival benefits of having fat stored.7

The second issue is due to adaptive thermogenesis—essentially, that metabolic energy expenditure declines with weight loss as the body attempts to “defend” its previous weight. Specifically, a 10% reduction in body weight causes a 20% to 25% decrease in 24-hour energy expenditure.7

Because this topic hasn’t been evaluated in the context of atypical AN, it’s unknown for what proportion of patients this is the case. However, Harrop and Jennifer L. Gaudiani, MD, CEDS-S, FAED, founder and medical director of the Gaudiani Clinic in Denver, say that lack of weight loss in atypical AN is not at all rare in their practices.

There’s no one definitive cause of AN or atypical AN; a complicated matrix of biological, sociological, and psychological factors likely drives the diagnosis. Genetic predisposition sets the stage, while environmental factors—such as messages from media, health organizations, health care providers, family, and peers—confer other various risk factors, such as a fear of weight gain and desire to be thin. This is especially true for young girls, more than 50% of whom take measures to control their weight before puberty.8 Regardless of eating disorder status, higher weight is associated with greater body dissatisfaction among adolescents.9

Restrictive eating disorders such as AN also have been found to co-occur with various mental health conditions, but there appears to be a particularly strong link with anxiety disorders and obsessive-compulsive disorder (OCD). According to the National Eating Disorders Association, 69% of patients with any type of AN also have OCD, while 48% to 51% have an anxiety disorder (eg, generalized anxiety disorder, panic disorder, social anxiety disorder).10 This correlation is thought to be due to shared personality-related traits, such as neuroticism, perfectionism, and a need for control.11

The National Eating Disorders Association states that no significant differences have been found in medical or psychological outcomes of AN vs atypical AN.2 Those with AN and atypical AN experience the same frequency and severity of malnutrition, leading to complications such as the following6:

• thinning or loss of hair;
• mental health conditions including anxiety, depression, and suicidal thoughts and behaviors;
• amenorrhea and hypogonadotropic hypogonadism (ie, decreased production of sex hormones);
• anemia;
• loss of bone and muscle mass and increased risk of osteoporosis and related conditions;
• gastrointestinal symptoms such as constipation, dysphagia, and gastroesophageal reflux disease; and
• cardiovascular conditions including extremely low heart rate and blood pressure, and arrhythmia.

With eating disorders, especially AN, comprising the second-highest proportion of mental illness–related deaths (often due to organ failure and CVD as a result of malnutrition, or to suicide), early intervention is imperative. Unfortunately, some studies have recorded a longer duration between onset of illness and treatment for those with atypical AN compared with their counterparts with AN, and/or that those with atypical AN are less likely to receive inpatient care. Using history of overweight or obesity as a proxy for atypical AN, Kennedy and colleagues discovered that, of 522 females (mean age 15.5 years) with AN or atypical AN, those with a history of overweight or obesity were less likely to have received inpatient care at a one-year follow-up, despite greater weight loss than those without such history.12

Among the sample of adults with atypical AN in Harrop’s research, the lower the BMI a participant reached, the faster they accessed treatment, and 28% had received no treatment for their condition at the time of the study. Time between onset and treatment averaged 11.7 years, though a wide range of durations was present (less than one year to 42 years).1

Barriers to Care
All of the experts Today’s Dietitian spoke with name weight bias as a significant, if not the most significant, barrier to care in atypical AN. And they describe it coming from all levels: practitioners, institutions, patients, and parents.

In Harrop’s extensive interviews with atypical AN patients diverse in age and gender and racial and sexual identities, all described experiences that most practitioners would find unethical. Primary care providers prescribed weight loss without inquiring about a patient’s ED history, or recommended calorie restriction despite that history. They attributed a patient’s medical concerns to higher weight without investigating whether symptoms could be the result of organic disease.1

Other patients, like Marie, were simply turned away by eating disorder professionals when they tried to seek care because of their size. They were told to “come back when they were sicker” or were disbelieved altogether.1

For example, Gaudiani describes receiving erroneous referrals from a primary care provider for a patient’s supposed binge eating disorder when the patient was suffering from the effects of severe restriction—“an error of visual assumption,” as she calls it.

Providers "look at people who are in larger bodies and they instantly make assumptions about how they’re eating and moving,” Gaudiani says. “I have patients with atypical anorexia nervosa who have been restricting calories for months, if not years, with no days off, and they are feverishly working out two hours a day—and they’re in a larger body. And the first thing the doctor says, without asking anything about them is, ‘You know, your weight’s pretty high; you probably need to cut what you eat and exercise more.’” Simply put, these practitioners don’t believe a higher-weight patient could be restricting.

Marci Evans, MS, CEDRD-S, LDN, owner of Marci RD Nutrition in Cambridge, Massachusetts, agrees. As a clinical supervisor for eating disorder RDs, she frequently addresses and discusses weight bias concerns with her practitioner clients. As practitioners, she says, "we live in a culture where we are so used to prescribing eating disorder behaviors to people in higher-weight bodies, and there is an expectation that higher-weight people should be starving themselves.”

Garber, who works with pediatric patients, has encountered similar challenges from young patients with atypical AN and their caregivers. “Patients themselves have internalized weight bias, and parents have weight bias that make it very, very difficult to establish gravity,” she says. “I [recently] had a patient in clinic … who was coming in with malnutrition, with rapid weight loss, and we were trying to impress upon [her] parents our clinical concern. And the parent said, in kind of a lower voice, ‘Quite frankly, she was a little chubby before, so we really don’t think this is an eating disorder.’ They were very focused on that instead of being able to accept or take in all of the clinical signs and symptoms of malnutrition that we were showing them.”

Significant disparities between insurance coverage for atypical AN vs AN are also a problem. According to Gaudiani, some insurance plans don’t cover eating disorder treatment, and even when they do, they don’t tend to include OSFED diagnoses. In other words, patients with an underweight BMI may have their AN treatment covered by insurance, but patients with a “normal” or higher BMI receiving the same treatment in the same facility rarely have that benefit.

Tips for Practitioners
RDs who encounter higher-weight patients with atypical AN might miss red flags if they’re not anticipating that these patients may report AN behaviors and views. The following are ways RDs can prime themselves and other providers to recognize atypical AN and create an environment for patients that fosters effective and sensitive care.

Follow the science and educate others. While weight is a deeply held metric widely perceived to determine AN severity, it simply is no longer an evidence-based one. Garber doesn’t advocate throwing weight out the window in the context of AN—weight gain is nearly always a clinical necessity for recovery—but it shouldn’t be used as a measure of severity. History of weight loss presents an alternative metric; several of Garber’s studies and others have found a strong correlation between greater recent and total weight loss and clinical measures of AN severity such as lower heart rate and lower serum phosphorus—all independent of presentation weight.13,14

“There have been a few other studies on weight loss history, but still I think the field at large is focused on weight at presentation,” Garber says. She prioritizes educating those who aren’t eating disorder professionals, such as pediatricians and primary care providers, on these results, identifying these practitioners as “our first line of defense” in recognizing and referring atypical AN patients.

That said, keep in mind that some patients will present with little or no weight loss, so neither presentation weight nor weight loss history should be used to the exclusion of other diagnostic measures.

Choose words carefully. Because fear of weight gain is so widespread and normalized, practitioners can inadvertently reinforce this fear in their patients. “When somebody with any-body-size anorexia says, ‘I’m afraid I’m going to get fat,’ it’s very common for well-meaning clinicians—I did it for years—to say, ‘You’re not going to get fat, don’t worry,’” Gaudiani says. In reality, “we have no idea what your body is going to do in recovery, and, whatever it does, as long as you’re caring for yourself, that’s the body that was meant to be, and we’ll then work on finding a way to accept that body.”

Part of this is also asking patients the right questions. While patients with atypical AN don’t have different symptoms and outcomes than those with AN, their experiences in the health care system, especially for those in larger bodies, probably have been traumatic.

“Those experiences—of not being believed, being gaslit—are traumatic,” Evans explains. “I have worked with a number of clients whose therapists identify as eating disorder specialists and then somehow lose their therapist hat when their client starts talking about their relationship to food and body.”

Harrop suggests asking patients explicitly what has been their previous experience with RDs and eating disorder professionals, as well as with seeking care, to recognize potential trauma. Carrie Dennett, MPH, RDN, CD, offers a thorough primer on trauma-informed nutrition care in the June/July 2021 issue of Today’s Dietitian.

Evans, Gaudiani, and Harrop also recommend asking the client how they might feel about seeing a thin practitioner. “It’s the job of the clinician to be able to own and discuss these things so we’re creating this kind of environment where … we’re not acting as if the body isn’t in the room, we’re letting them know this is something we’re very comfortable with and we’re normalizing a space where we’re addressing the power differential between the clinician and the client,” Evans says. “The client hopefully over time feels more and more comfortable speaking their truth and maybe giving feedback to the clinician.”

Create an inclusive environment. RDs can help create spaces that are welcoming to all bodies. Be sure educational materials such as pamphlets, decorative artwork, and images on your website aren’t only or predominantly “celebrating thin people cavorting around doing able-bodied things,” Gaudiani says. “Make sure that seating is all-body-friendly.”

For example, practices should provide chairs without arms and wide and accessible doorways.

• Practice humility and expect mistakes. Certainly, not all practitioners openly express doubt about a higher-weight patient’s restrictive behavior. But unconscious attitudes about weight can get in the way of diagnosis and care, too, experts emphasize. Even practitioners who are acutely aware of weight biases make mistakes.

“How a patient presents colors how we do an assessment,” Harrop says. “It colors what questions we ask. When I counsel clients, I have a basic assumption that … I’m going to make weight-stigmatizing errors. Not because I want to make those errors but because I’m a fallible person. Despite the work I’ve done in the weight stigma space, these weight-stigmatizing attitudes still pop up.”

Gaudiani agrees: “I constantly find myself tripping over my own internalized weight bias,” she says. “I routinely check a DXA [dual-energy X-ray absorptiometry] bone scan in my patients who have had anorexia nervosa. And yet once or twice, when working with a patient with atypical anorexia nervosa, I failed to check bone density because I had that implicit internalized bias that their larger bodies are safer” and confer less risk of negative AN outcomes.

Evans asks RDs, including those to whom she acts as a clinical supervisor, to consider, “If you can imagine you don’t know anything about this person’s body size, and you’re just listening to their words and their experience, how would you treat them and what would your interventions be? I think that can be a really helpful spot check.”

It can be helpful to investigate one’s own attitudes toward higher-weight people to try to recognize and “weed out” these gut reactions against larger bodies. “I encourage clinicians to imagine how they might feel or react if their body was to change significantly in the weight gain direction, what sorts of thoughts or fears might be generated in them,” Evans says. “That can sometimes reveal where the fat-phobia is tucked inside of them.”

Further resources on weight bias can be found in the sidebar on page 44.

Final Thoughts: Working Together
Some RDs may find a discussion of weight bias polarizing and eschew frameworks such as Health at Every Size® (HAES®), viewing some activists’ statements (eg, “Weight has no bearing on health”) as not evidence based. But there’s more common ground between HAES® and ethical standards of care than meets the eye, Evans emphasizes, and weight-inclusive care doesn’t necessarily have to be an all-or-nothing approach.

She suggests “finding a sweet spot to where we can integrate health-promoting behaviors that support overall well-being as opposed to a singular objective marker like weight. I think that for most people I speak with, [even those who resist HAES®], that’s very reasonable.

“I would encourage clinicians to listen and trust the experience of their clients rather than getting distracted by the size of their body. People in higher-weight bodies are suffering mentally, emotionally, and physically, in all the same ways clients in lower-weight bodies do. They deserve and need our clinical skill, our compassion, our belief in them, our respect.”

— Hadley Turner is associate editor for Today’s Dietitian and, the blog written for RDs by RDs.


Weight Bias & Eating Disorder Resources

The Body Is Not an Apology, 2nd Edition: The Power of Radical Self-Love by Sonya Renee Taylor

Radical Belonging: How to Survive + Thrive in an Unjust World (While Transforming It for the Better) by Lindo Bacon, PhD

Fearing the Black Body: The Racial Origins of Fat Phobia by Sabrina Strings

Sick Enough: A Guide to the Medical Complications of Eating Disorders by Jennifer L. Gaudiani, MD, CEDS-S, FAED

What We Don’t Talk About When We Talk About Fat by Aubrey Gordon

“The Problem With Weight Loss” (three-part series) by The Dr. John Berardi Show

1. Harrop E. “Maybe I Really Am Too Fat to Have an Eating Disorder”: A Mixed Methods Study of Weight Stigma and Healthcare Experiences in a Diverse Sample of Patients with Atypical Anorexia [PhD thesis]. Seattle, WA: University of Washington; 2020. Accessed May 5, 2021.

2. Anorexia nervosa. National Eating Disorders Association website. Accessed June 2, 2021.

3. Stice E, Marti CN, Rohde P. Prevalence, incidence, impairment, and course of the proposed DSM-5 eating disorder diagnoses in an 8-year prospective community study of young women. J Abnorm Psychol. 2013;122(2):445-457.

4. Masheb RM, Ramsey CM, Marsh AG, Snow JL, Brandt CA, Haskell SG. Atypical anorexia nervosa, not so atypical after all: prevalence, correlates, and clinical severity among United States military veterans. Eat Behav. 2021;41:101496.

5. Sawyer SM, Whitelaw M, Le Grange D, Yeo M, Hughes EK. Physical and psychological morbidity in adolescents with atypical anorexia nervosa. Pediatrics. 2016;137(4):e20154080.

6. Rastogi R, Rome ES. Restrictive eating disorders in previously overweight adolescents and young adults. Cleve Clin J Med. 2020;87(3):165-171.

7. Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. Int J Obes (Lond). 2010;34(0 1):S47-S55.

8. Attia E, Walsh BT. Anorexia nervosa. Merck Manual, Professional Version website. Updated June 2020. Accessed June 1, 2021.

9. Calzo JP, Sonneville KE, Haines J, Blood EA, Field AE, Austin SB. The development of associations among body mass index, body dissatisfaction, and weight and shape concern in adolescent boys and girls. J Adolesc Health. 2012;51(5):517-523.

10. Eating disorders & co-occurring conditions. National Eating Disorders Association website. Accessed June 1, 2021.

11. Pollack LO, Forbush KT. Why do eating disorders and obsessive compulsive disorder co-occur? Eat Behav. 2013;14(2):211-215.

12. Kennedy GA, Forman SF, Woods ER, et al. History of overweight/obesity as predictor of care received at 1-year follow-up in adolescents with anorexia nervosa or atypical anorexia nervosa. J Adolesc Health. 2017;60(6):674-679.

13. Garber AK, Cheng J, Accurso EC, et al. Weight loss and illness severity in adolescents with atypical anorexia nervosa. Pediatrics. 2019;144(6):e20192339.

14. Whitelaw M, Lee KJ, Gilbertson H, Sawyer SM. Predictors of complications in anorexia nervosa and atypical anorexia nervosa: degree of underweight or extent and recency of weight loss? J Adolesc Health. 2018;63(6):717-723.