The word anorexia likely brings to mind the image of a dangerously underweight young female. However, this stereotypical image may miss the mark just as much as do assumptions about people with obesity who are nonetheless in excellent health, and those at a “normal” weight who have the metabolic profile of someone very sick. The former is referred to as “metabolically healthy obesity,” and the latter as “normal weight obesity.” These seemingly paradoxical categories have a parallel in atypical anorexia. Let’s take a closer look at this condition.

The National Association of Anorexia Nervosa and Associated Disorders (ANAD) describes atypical anorexia as “meeting all of the symptoms of Anorexia with weight at or above normal range.” Essentially, individuals with atypical anorexia may engage in the same behaviors as those with more typical anorexia, yet not experience the severe weight loss that often accompanies the disorder. Or, if they do experience substantial weight loss, they may have started out overweight or obese, so even after a potentially dangerous and rapid loss, their body mass index (BMI) is still classified as above normal.

In an article covering myths about atypical anorexia on the website of the National Eating Disorders Association (NEDA), an individual living with the condition notes that one myth is that people with atypical anorexia have a normal body size or are just slightly over the weight limit that might result in an anorexia diagnosis. The author also points out it’s a myth that the health consequences of atypical anorexia are not as serious and severe as those for underweight individuals with anorexia. She wrote that atypical anorexia is “not a diagnosis only reserved for the select few who are just a few pounds over the recommended BMI cutoff for anorexia. No. This diagnosis encompasses a huge swath of people of varying weights.”

It’s important to emphasize that body weight is not always a reliable indicator of health status and the severity of eating disorder behavior, because individuals who don’t fit the stereotypical profile may not receive the care they need. Not being dangerously underweight doesn’t mean someone is consuming an adequate amount of total food energy and nutrients, nor does it mean they’re not at risk for various physical and psychological comorbidities.

A paper published last month in the journal Pediatrics found that patients with atypical anorexia (who are at a normal weight, overweight or obese) experience similar cardiovascular and other health issues as anorexia patients with a low BMI. The study involved subjects age 12 to 24 with either anorexia or atypical anorexia (91% female, 50% Caucasian in the atypical anorexia group, 66% Caucasian in the anorexia group) enrolled in a randomized clinical trial. Independent of admission weight, faster prior weight loss was associated with lower heart rate and a greater total amount of weight loss was associated with lower serum phosphorus. The authors wrote, “Weight history was independently associated with markers of malnutrition in inpatients with restrictive eating disorders across a range of body weights and should be considered when assessing illness severity on hospital admission.”

Compared to those with anorexia, subjects in the atypical group scored significantly higher in a questionnaire assessing disorder psychopathology, which included “avoidance of food and eating, preoccupation with calories and eating in secret, feelings of fatness and discomfort seeing one’s body, dissatisfaction with weight and reaction to being weighed.” In a press release about the study, the lead author, Andrea Garber, Ph.D., RD, who is chief nutritionist for the UCSF Eating Disorders Program, said, “One possibility for the more extreme eating disorder behaviors and cognitions among the atypical group is that some of the patients had been overweight and may have suffered stigma or teasing that made them feel worse about their size. Or, if they were genetically predisposed to be on the heavier side, they may have had to employ more severe behaviors or have more severely disordered thoughts in order to fight their biology.”

Dr. Garber also noted, “patients with large, rapid or long duration of weight loss are more severely ill, regardless of their current weight.” The degree of illness has less to do with absolute body weight than it does the rapidity or amount of prior weight loss. In this study, the average BMI for the anorexia group at their heaviest was 20.7 (the low end of the healthy range), and 25.2 for those with atypical anorexia (the low end of the overweight range). At the time of hospital admission, however, average BMI for the typical group was 15.7 and 19.4 for the atypical group. So even upon admission, patients with atypical anorexia were still within the normal BMI range, albeit at the low end. And a plummet from an average BMI of over 25 to 19 certainly indicates a dramatic weight loss, even if 19 is still within the normal range. It’s worth noting this because there are people living with atypical anorexia who are overweight or obese, and who may be less suspected of having a restrictive eating disorder and the medical risks that come with it.

This study corroborates the findings of earlier research that determined that total weight loss and recent weight loss were better predictors of physical complications compared to weight at hospital admission in adolescents with restrictive eating disorders, including atypical anorexia. Research has also concluded that morbidity among adolescents with atypical anorexia is no less severe than that among those with typical anorexia, and that afflicted individuals in both groups experience depressive symptoms, obsessive-compulsiveness, self-harm or suicidal ideation, binge eating, laxative misuse, self-induced vomiting, and compulsive exercise.

It’s inappropriate to make assumptions about an individual’s dietary and exercise habits based solely on their body size. Just as overweight patients may be healthy and normal-weight patients may be living with metabolic illness, being at a normal weight, overweight, or obese does not rule out the presence of an eating disorder. Medical and nutrition professionals should remain vigilant for problematic behaviors in patients of all sizes.