BOSTON,March 8,2024 – Nearly 70% of American adults could be considered obese under updated criteria,a significant jump from the roughly 40% estimated using conventional body mass index (BMI) measurements. Researchers at Mass General Brigham say the new definition, developed earlier this year by the Lancet Diabetes and Endocrinology Commission, highlights the importance of considering body fat distribution, not just weight and height.
A Broader View of Obesity: Why the Numbers Are Shifting
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A new framework for defining obesity could dramatically increase the number of Americans identified as having the condition, prompting a reevaluation of treatment strategies.
- The updated definition incorporates waist circumference, waist-to-height ratio, and waist-to-hip ratio alongside BMI.
- Individuals with a normal BMI can now be classified as obese based on these anthropometric measures alone.
- The study of over 300,000 people revealed a particularly pronounced increase in obesity rates among older adults.
- Those newly identified as obese face a higher risk of diabetes, cardiovascular disease, and mortality.
The new guidelines categorize obesity based on both BMI and anthropometric measures – measurements of body size and proportions. Individuals with a high BMI plus at least one elevated anthropometric measure are classified as having “BMI-plus-anthropometric obesity.” People with a normal BMI can also be classified as having obesity if they have at least two elevated anthropometric measures,referred to as “anthropometric-only obesity.” The guidelines further separate obesity into preclinical and clinical forms, with clinical obesity defined by obesity-related physical impairment or organ dysfunction. The new standards have already been endorsed by at least 76 organizations, including the American heart Association and The Obesity Society.
Study Data Show a Sharp Rise in Obesity Rates
Researchers analyzed data from more than 300,000 participants in the National Institutes of Health All of Us Research Program. Using the new definition, 68.6 percent of participants met the criteria for obesity, compared with 42.9 percent under the traditional BMI-based approach. The entire increase was attributed to individuals classified as having anthropometric-only obesity. obesity rates differed across sex and race, but age showed the largest effect, with nearly 80 percent of adults over 70 meeting the new criteria.
higher Health Risks in Newly Identified Groups
The study also found that people with anthropometric-only obesity, who wouldn’t have been labeled as obese under older standards, had higher rates of diabetes, cardiovascular disease, and mortality compared with individuals without obesity. Roughly half of all participants who met the new obesity definition were categorized as having clinical obesity. This percentage was only slightly lower among those with anthropometric-only obesity than among those with BMI-plus-anthropometric obesity.
“We have always recognized the limitations of BMI as a single marker for obesity as it doesn’t take into account body fat distribution,” said senior author Steven Grinspoon, MD, Chief of the Metabolism Unit in the Endocrinology Division of the Mass General brigham Department of Medicine.”Seeing an increased risk of cardiovascular disease and diabetes in this new group of people with obesity, who were not considered to have obesity before, brings up captivating questions about obesity medications and other therapeutics.”
What This Means for Treatment and Future Research
The researchers note that additional studies are needed to better understand why anthropometric-only obesity develops and which treatments might potentially be most effective.The team has previously developed a therapy aimed at reducing waist circumference and plans to evaluate how different treatment strategies might benefit this newly defined group.
“Identifying excess body fat is very significant as we’re finding that even people with a normal BMI but with abdominal fat accumulation are at increased health risk,” Fourman said. “Body composition matters – it’s not just pounds on a scale.”
