Industry Voices—We can't fight obesity with a ballpark estimate

Imagine an engineer using rough estimates to build a bridge. Instead of determining precise measurements for the safest bridge, they opt to use the ballpark estimates from a prior one. The engineer would have little understanding of the unique dimensions of the project, and construction would likely be faulty at best. People might even be at risk of falling through the cracks on their journey across.

Successful engineering, like high-quality medical care, calls for precision. The best doctors collect as much information as they can about a patient’s health to inform their decisions. That’s why it’s shocking that today our health system defaults to a ballpark estimate when measuring a chronic condition that affects more than 40% of adults—obesity.

The measure used is BMI, or body mass index. It was adopted as the go-to for diagnosing obesity in the 1980s and hasn’t been updated since. If the health system continues to rely on it, like a poorly built bridge, some people will fall through the cracks, missing out on the opportunity to prevent or treat obesity.

No better time than now

There is greater urgency than ever to reevaluate the use of BMI as a primary measure because we’ve been handed a powerful new tool in the fight against obesity. This tool comes in the form of several incredibly effective, new prescription treatments called glucagon-like peptide 1 (GLP-1) receptor agonists—for instance, Novo Nordisk’s Wegovy.

People on GLP-1 treatment supported by lifestyle changes can expect to lose 15% of their body weight on average over the course of a year—with medications on the horizon promising 20% or more. Here’s the problem: doctors are prescribing, and insurance companies are choosing to cover these GLP-1 treatments primarily based on an individual's BMI. If this continues, inevitably, some people will not get the medical care and potentially life-changing treatment they deserve.

Flawed history and an incomplete picture

The history of BMI gives evidence to its shortcomings. The idea was introduced in the 1830s by Adolphe Quetelet, a mathematician who sought to define the measurements of the “average man.” He considered anything beyond those measures a “deformity” or even “monstrosity.” Fast-forward to 1972, when scientist Ancel Keys gave Quetelet’s equation the name we know—Body Mass Index—and stated that BMI is “as good as any” tool for measuring relative obesity, though it may be “not fully satisfactory.”

Keys’ observation was an understatement. While BMI is useful in assessing the weight-related health of a population, it’s not as useful at the individual level. BMI standards don’t apply in the same way to all people. BMI is based on data in White people—so it’s better at describing health risks in White populations. Meanwhile, Asian and South Asian Americans see health problems at lower BMIs than White Americans. Further, research shows that Black Americans—especially Black women—don’t experience increased risks until BMIs that are higher than current overweight and obesity cutoffs.

BMI can also be misleading. Healthy muscle is denser than body fat, so it weighs more. And importantly, body fat around the belly, called visceral fat, is riskier than body fat elsewhere. Unfortunately, BMI can’t identify either of these factors. Tall, fit athletes with lots of lean muscle, daily exercise, and good cholesterol levels can have an “overweight” BMI. Meanwhile, a college student who smokes, rarely exercises, and replaces meals with potato chips can have a BMI that is “ideal.”

More precise measures

While measuring BMI is one step in defining obesity, it’s best when paired with tools that give patients, their doctors, and insurers a clearer picture of each individual’s health. Studies show that a person’s waist-to-hip ratio—which identifies belly fat—is a stronger predictor of death from any cause when compared to BMI. The Edmonton Obesity Staging System (EOSS), an in-depth look at metabolic, physiological and mental health factors, offers a more complete assessment of weight-related health.

Since people with obesity live with higher risks for developing many other diseases, it’s important to look for risk factors alongside someone’s BMI. This includes common screenings such as blood sugar, blood pressure, cholesterol levels, and kidney function. While BMI has long been valued for its simplicity, these alternatives can also be relatively easy to measure.

Putting trust in BMI alone means identifying some people as having unhealthy overweight or obesity when their bodies are healthy—while others with “normal” BMIs slip under the radar. As such, people will lose the chance to prevent disease before it sets in—both obesity and the many conditions connected to it.

We cannot possibly respond to an epidemic of this proportion if we rely solely on this ballpark estimate to diagnose and decide who gets access to treatment. Let’s get precise, individualized, and comprehensive in how we care for those with obesity. No one should risk falling through the cracks on their health journey.

Steve Silvestro, M.D., senior manager of medical content and education at Ro, is a board-certified pediatrician who previously spent more than a decade in practice during which he treated many children, teens, and young adults with overweight and obesity. Silvestro completed his medical training and residency at Georgetown University.