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In 2024, the European Association for the Study of Obesity (EASO) published an updated framework for classifying obesity that recognizes that the use of BMI is a limited tool in defining the condition.

The organization’s new tool and its goal of promoting “the holistic treatment of obesity by combining both anthropometric and clinical components in its definition of obesity” call for combining BMI with the measurement of waist circumference to height and assessing for the presence of other comorbid physical or psychological conditions — using those three factors together to define obesity.

And while EASO researchers’ goal was to improve obesity management through personalized treatment similar to those for other chronic diseases, the results had another effect. 

Researchers at Adelson School of Medicine at Ariel University, Ariel, Israel, found that nearly 1 in 5 Americans previously considered overweight would now be classified as obese if evaluated according to the new EASO guidelines. Their results were published last month in Annals of Internal Medicine.

Despite having lower BMI measurements, these individuals face serious health risks, including hypertension, diabetes, heart disease, and much more. Lead author of the Israeli study, Orna Reges, PhD, epidemiologist and the director of the epi-cardio research lab at the Adelson School, said the survey demonstrates that these individuals and others like them may benefit from more personalized follow-up care.

“Since more than half of overweight individuals are now classified as living with obesity and are at increased risk of mortality, it is essential to examine whether they may benefit from targeted treatments,” Reges said. “Further studies are needed to support these findings, enable personalized treatment of obesity, and help reduce obesity-related complications and mortality.”

Implications for Everyday Clinical Practice

Dympna Gallagher, EdD, professor of nutritional medicine at the Columbia University Vagelos College of Physicians and Surgeons and co-director of the New York Nutrition Obesity Research Center at Columbia University, New York City, said the Adelson study “has done a very nice job in showing where this (the new EASO framework) has merit.”

She noted that in evaluating the implications of the Adelson study, the next question to ask is whether all individuals in the obesity range have comorbidities and cautioned that it’s not necessarily the case.

“There are those who have one, but it’s maybe not life-threatening. There are those who have multiple,” she said. “Typically, the prevailing notion is risk is much less in individuals who have normal weight. However, there are also individuals who fall into that normal weight category who have risk factors — for example, people with normal weight, but for their weight, they may have great excess adiposity relative to their weight.”

It’s in this context that Gallagher said clinicians can use the new EASO framework and the indication of increased individuals at risk as highlighted by the Ariel University study to “red flag” individuals who need to be surveilled with greater sensitivity.

Gallagher highlighted the difference between the EASO study’s use of waist-to-height ratio and waist-to-hip ratio, which is more commonly known in obesity literature.

“Waist-to-height ratio tries to get at fat distribution. The greater waist circumference relative to your height, the greater the likelihood that you have visceral adiposity, or fat that’s accumulated intra-abdominally, which is known to be associated with increased metabolic rate risk,” Gallagher said. “If you pinch your abdomen, the outer layer is subcutaneous fat, which is just underneath the skin. Inside that is a layer of muscle, your abdominal muscle, and then inside that with all of your organs is more fat that we refer to as visceral adipose tissue.”

Subcutaneous and visceral adipose tissue are metabolically two different types of fat, and visceral adipose tissue is associated with much greater metabolic risk.

In terms of primary care practitioners and other clinicians applying this data in their day-to-day work, Gallagher said the framework should be a relatively easy lift for clinicians and then can be used to determine an indication for clinical follow-up.

Measurements can easily be done in a physician’s office. So, right there, Gallagher said, “the physician can get a sense of, okay, how many risk factors this person may have,” she said.

Don’t Let the Perfect Be the Enemy of the Good

Nathaniel Villanueva, MD, who treats bariatric patients at the Plastic Surgery Institute in Beverly Hills, California, said that while anthropomorphic-based assessments aren’t perfect, the new EASO framework is an improvement in alerting for obesity and the related conditions that go along with it.

“Although these studies will never be completely accurate when only using a few measurements and weight to determine long-term prognosis related to body weight and obesity, it is a move in the right direction to not just use BMI in the classification of obesity,” he said.

There are people with high BMI but also higher muscle density and lower body fat who should be classified as obese, he said. At the same time, there are those with decent BMI but with a waist-to-height ratio greater than 0.5, which is a significant indicator of higher body fat percentage.

“The inclusion of comorbidities like hypertension and diabetes, which are also significantly associated with higher body fat percentages, makes the scale much more accurate and a better predictor for long-term health and prognosis in the treatment and management of obesity,” Villanueva added.

With these factors in mind, Villanueva agreed with the assessment that use of this framework in clinical practice will help to ensure that individuals who may need treatment don’t fall through diagnostic cracks.

“It opens the opportunity to identify individuals who were not previously considered at higher risk to inform them and guide them in order to reduce risk of long-term health problems associated with obesity,” he said.