A Dietitian Weighs In On The Limitations of BMI —And How New Guidelines Are Baby Steps In the Right Direction, Particularly for Eating Disorder Treatment

Just last week, a client shared that fixating on the body mass index (BMI) is what’s holding her back from finding peace with her body—and she is certainly not alone. As a weight-inclusive, eating disorder dietitian, I can, unfortunately, recall countless clients and patients who feared visiting a healthcare provider because they expected to be shamed if their BMIs fall out of the “normal” range.

The BMI—which is a simple calculation measuring body fat based on height and weight—was created around 200 years ago by a Belgian mathematician to quickly measure “obesity”* of the general (mostly white, male) population—not to determine an individual’s health.

By the 1970s, it wrongly became one of the most common ways to assess a person’s “health” and diagnose illnesses, including eating disorders. Here is what you need to know about BMI including the American Medical Association’s (AMA) new guidelines.

Here’s the Gist of the New Guidelines

This summer, the AMA published new guidelines urging physicians to stop using BMI as the end-all-be-all tool in their assessments and diagnoses. The AMA’s guidelines were preceded with an evaluation of the BMI’s “problematic” history and discusses alternatives to the BMI. Here are some of the key points made:

• BMI does not represent racial and ethnic minorities.
• The BMI doesn’t consider other pertinent variables like gender and age.
• It’s being inappropriately used in clinical settings and to predict mortality in population-based studies.
• BMI can be harmful to those with eating disorders because it does not “accurately capture” manifestations and diagnoses of eating disorders outside of textbook anorexia nervosa.
• The AMA reports that using BMI can prevent access to eating disorder treatment and lead to “substandard eating disorder treatment, typically due to the use of BMI by insurance companies to cover inpatient treatment.”

BMI and Eating Disorders

The AMA also made specific recommendations when it comes to eating disorders. Here’s what the guidelines propose:

• Train all “school-based” doctors, counselors, teachers, nurses, coaches, and trainers to spot unhealthy, abnormal eating behaviors, as well as dieting and weight-restrictive behaviors in teens.
• Educate and refer teens and their families for evidence-based and culturally-informed counseling when necessary.
• Use appropriate, culturally-informed resources and counseling tools about unhealthy eating behaviors and restrictions.
• Refrain from using BMI as a sole criterion for appropriate insurance reimbursement, in some diagnostic circumstances.

Fellow eating disorder dietitian Lauren Chaffin, MS, RD, LD, says the BMI scale can be harmful to those with eating disorders and can even play a role in the development of their harmful eating patterns. For example, for those with a restrictive eating disorder resulting in a low weight, achieving a normal weight according to BMI can give the false presumption that they are healed of their disorder, when, the opposite can be true, Chaffin says.

“Likewise, there are many people who suffer from a restrictive eating disorder, yet remain in a larger body and as such, a higher BMI, causing them to not be taken seriously and treated harmfully at the doctor’s office,” she adds.

The Pros of the New AMA Guidelines

According to eating disorder dietitian Jaclyn Leocata, MS, RDN, CDN, the new guidelines are a step in the right direction toward decreasing the emphasis on BMI in clinical settings. Not only does it acknowledge the sexist, racist, and ageist roots of the BMI, but these new guidelines also indicate the necessity for culturally-informed providers and resources and recognize that mortality should be linked to metabolic health (i.e., insulin resistance, cholesterol, and blood pressure)—not BMI.

When it comes to eating disorders, Kara Pepper, MD, LLC, an eating disorder specialized physician says that other positives of the guidelines include acknowledging that eating disorders are a product of overemphasis on the treatment of obesity and recommending multidisciplinary screening for disordered eating behaviors.

Although eating disorders are mental illnesses experienced by people of all body sizes (and BMIs), research shows that weight stigma (negative beliefs and actions toward people in larger bodies) among clinicians—including the use of BMI—negatively impacts eating disorder diagnosis, treatment, and recommendations.

“These new guidelines bring attention to something providers in the field of eating disorders have long recognized: patients may have significant medical or nutritional concerns that are not dependent on presentation weight or BMI,” adds Anna Tanner, MD, FAAP, FSAHM, CEDS-S, Vice President of Child and Adolescent Medicine for Veritas Collaborative and The Emily Program.

That said, Dr. Tanner does not believe the guidelines will help to improve eating disorder prevention, diagnosis, and/or treatment. “However, this statement is a good first step in breaking down misperceptions that directly conflate weight and health.”

The Cons of the New AMA Guidelines

There still seems to be a long way to go toward more humane and evidence-based healthcare. While the guidelines explore other ways to evaluate health, they also include weight-focused alternatives that continue to perpetuate harmful and weight-stigmatizing healthcare practices.

“Unfortunately, the new statement continues to focus on the detection of ‘obesity’ and directs providers to continue to focus on additional weight-related measures such as ‘measurements of visceral fat, body adiposity index, body composition, relative fat mass, waist circumference, and genetic/metabolic factors,'” adds Dr. Tanner. “These assessment criteria perpetuate the idea that we can fully ‘measure’ health.”

Further, the guidelines recommend that physicians adopt the idea that obsessing about thinness is as dangerous to a person’s physical and mental health as “obesity,” which implies that being at a higher weight makes a person physically and mentally unwell. “I feel that weight stigma and bias need to be addressed in the clinical setting before the new guidelines would have any impact on eating disorder care,” says Leocata.

In fact, such weight stigma can be the factor causing harm to a person’s health—not their weight. For example, research shows weight discrimination can increase allostatic load or the combined effects of chronic stress on holistic health.

“If the recommendation is to continue to include other resources to focus on body size/composition it is just another way for providers to focus on and continue to recommend intentional weight loss,” adds Leocata. “This, in turn, will continue to result in more disordered eating, weight cycling, and eating disorders.”

Dr. Pepper points out that the guidelines still note BMI is needed for eating disorder diagnosis and the recommendations for eating disorder detection are for teens, which “misses the millions of adults who struggle with eating disorder behaviors.”

So, What’s the Alternative to BMI?

Something not mentioned in the new guidelines is that there are weight-inclusive ways to assess a person’s health and accurately diagnose, prevent, and treat life-threatening illnesses like eating disorders, which are supported by research.

“No measurement should be a primary determinate of health, and medicine must move past the concept that health can be measured,” explains Dr. Tanner. “Instead, medical providers must learn to take a very individualized approach to assessing health.”

Providers and patients can explore the Association for Size Diversity and Health’s alternative, evidence-based paradigm—called Health at Every Size. It offers a framework of principles, including weight inclusivity and body diversity, eating for wellness and pleasure, respectful non-stigmatizing care, and more.

While the weight-centric paradigm (which includes regular use of the BMI) focuses on physical health and weight, the weight-inclusive approach looks at the whole person and considers factors like financial, social, and occupational health. As a weight-inclusive provider, Leocata recommends assessing a person’s behaviors, like food intake and variety, physical activity, stress, and sleep patterns while Dr. Tanner suggests reviewing lab results, vital signs, and hormonal health.

“Additionally, what concerns does this person have about their shape and weight and how does this influence their eating and exercise behaviors and their body satisfaction?” says Dr. Tanner. “Medical concerns can be found when eating disorder behaviors are present without a change in weight. Conversely, persons with a ‘concerning’ BMI may have very good health across these medical and psychological domains.”

Personally, I honestly pay no attention to a client’s BMI. What I do care about is my client’s holistic wellness, which usually includes vital signs (blood pressure, heart rate, and sometimes weight), lab values, nutritional intake, body cues, emotional well-being, self-care, nervous system regulation, food and exercise behaviors, and their relationships to food, body, and exercise.

Dr. Tanner emphasizes that clinicians can make false health assumptions about eating disorders based on weight and BMI. “Providers must be trained to look for eating disorder behaviors—restriction, purging, binge eating, and selective eating—and recognize that these behaviors may be present in any patient, at any age, weight, or gender.”