One in five American adults, over 50 million people who were previously defined as overweight based on BMI alone, were now considered persons with obesity (PWO) under the new definition adopted by the European Association for the Study of Obesity (EASO).
A study by a team from Ariel University published a broad study on Tuesday in the Annals of Internal Medicine, claiming that BMI alone no longer tells the full story
The practical conclusion of the study was that millions who described themselves as "just a little overweight” could now be suffering from a weight problem and all the medical implications that come with that.
While the research focused on the U.S. population, the findings are relevant to Israel as well. Thousands of Israelis who were not previously diagnosed with obesity may now fall into a high-risk category for illness and death, and could require early medical intervention.
“We now understand that obesity is not just a number on the scale, but a complex chronic disease with significant health implications,” said Prof. Dror Dicker, an obesity specialist and head of Internal Medicine D at Sharon Hospital. “The new definition may allow us to identify high-risk patients at an earlier stage and prevent the development of life-threatening conditions.”
New obesity definition may classify more as high-risk, Experts Say
The new diagnostic framework adopted EASO could reclassify many individuals currently considered overweight as obese, if they have significant abdominal fat. Under this approach, people with a body mass index (BMI) between 25 and 30 may be diagnosed with obesity if their waist-to-height ratio exceeds 0.5 and they also suffer from an obesity-related condition.
The EASO’s revised definition incorporates additional anthropometric measures beyond BMI and takes into account the presence of related illnesses. But, the framework has not been scientifically validated.
“BMI has many limitations," Dicker said “For example, muscular individuals may score high on BMI even if they’re not obese. It also doesn’t account for fat distribution, such as women who carry excess weight in the hips. That’s why researchers around the world are working to develop more accurate measures to diagnose obesity.”
Dicker said the goal is to detect obesity at an early stage, before it causes hear disease or other health complications. “This is precisely why the new definition was developed by European experts and it’s what we aimed to apply in our study," he said.
High rates of illness and mortality
Researchers from Israel's Ariel University, Tel Aviv University and Holon Institute of Technology analyzed data from 44,030 American adults who participated in the U.S. National Health and Nutrition Examination Survey (NHANES) between 1999 and 2018. The study assessed complications and mortality risk under the new definition of obesity.
According to the findings, 18.8% of participants who were previously classified as merely overweight based on BMI are now considered people with obesity (PWO) under the revised criteria. Among this group, common conditions included high blood pressure (79.9%), arthritis (33.2%), diabetes (15.6%) and cardiovascular disease (10.5%).
Despite the high rate of illness, the newly classified group did not show an increased risk of death compared to adults of normal weight. However, individuals with a BMI of 30 or higher who were considered obese under traditional criteria had a nearly 20% higher mortality risk. The elevated rates of illness did not translate into higher mortality unless compared with individuals of normal weight and no underlying health conditions.
The potential impact on treatment
“Compared to people of normal weight with no underlying conditions, the risk of death among individuals classified as living with obesity under the new definition is 50% higher, similar to the risk observed in people of normal weight but with underlying illnesses.” Dr. Thomas Kraptí, a physician and data scientist at the Holon Institute of Technology, said. “When compared to those still classified as overweight, the mortality risk is 77% higher.”
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Prof. Orna Reges, an epidemiologist and researcher in the Department of Health Systems Management at Ariel University, said that since more than half of those previously considered overweight are now classified as obese, they may benefit from targeted treatments.
Dicker said the findings were also relevant for the Israeli population. “There are many people in Israel who are not formally diagnosed with obesity, but under the new definitions would be considered as living with the condition and their risk of mortality increases as a result.”
Dicker also pointed to a study that was published in the Lancet earlier this year, conducted by the late Dr. Maj. Yair Zaluf, who was killed in the war that showed that teens who were overweight when they joined the IDF, were 20% to 27% more likely to develop obesity within five years, compared to peers with a normal weight.
“That’s why it’s so important to identify individuals at risk as early as possible—using the same ‘new’ criteria our study is based on,” Dicker said.