Obesity Rates Rise to 70% with New Definition, Study Finds

'Astounding': 70% of adults may be considered obese under new definition of condition

COULD ACTUALLY BE MUCH MORE ACCURATE. A MARY SALADNA IS IN THE NEWSROOM AND MARY THE RESULTS AREN’T GOOD. NO, THEY’RE NOT, BUT THE RESULTS ARE MORE REALISTIC AND MORE PROOF THAT BODY COMPOSITION MATTERS, NOT JUST POUNDS ON A SCALE. TRADITIONALLY, WE’VE RELIED ON BMI TO DIAGNOSE OBESITY AND THE HEALTH RISKS ASSOCIATED WITH EXCESS FAT. BUT A NEW DEFINITION FACTORS IN BODY FAT DISTRIBUTION, SUCH AS THE SIZE OF YOUR WAISTLINE AND BY THAT DEFINITION, OBESITY AMONG AMERICANS JUMPS FROM ABOUT 40% TO NEARLY 70% OF ALL ADULTS. YOU KNOW, THAT’S MORE PEOPLE IN AMERICA HAVING OBESITY THAN NOT HAVING OBESITY. DOCTOR LINDSAY FORMAN COAUTHORED THIS STUDY. SO IF YOU’RE, LET’S SAY, A BMI OF 23, SOMEONE THAT YOU WOULD CONSIDER THIN, BUT HAVING AN INCREASED WAIST CIRCUMFERENCE OR WAIST TO HIP RATIO, YOU WOULD NOW BE CLASSIFIED AS HAVING OBESITY. THE EXPANDED CRITERIA MEANS MILLIONS MORE AMERICANS COULD BE AT RISK FOR OBESITY RELATED HEALTH COMPLICATIONS LIKE DIABETES AND HEART DISEASE, AND THE GOAL IS TO IDENTIFY PEOPLE AT RISK AND HELP THEM. I THINK PEOPLE REALIZE LIKE, OH, I HAVE A LOT OF FAT IN MY BELLY. YOU KNOW, WHILE I MIGHT BE THIN AND HAVE THIN LEGS, IT’S LIKE HARD TO FIT INTO MY PANTS. BELLY FAT IS A COMMON PROBLEM, PARTICULARLY FOR WOMEN AFTER MENOPAUSE AND FOR ALL OF US AS WE AGE. IN FACT, THE STUDY ALSO FOUND THAT IN OLDER AMERICANS OVER AGE 70, CLOSE TO 80% OF AMERICANS ARE LIVING WITH OBESITY. USING THE NEW CRITERIA. AND YOU KNOW, THAT HAS MAJOR IMPLICATIONS IN TERMS OF HEALTH PAYER SYSTEMS LIKE MEDICARE. WHO IS GOING TO BE ELIGIBLE FOR OBESITY MEDICATION? IS IS AN ALREADY A VERY HOT POTATO QUESTION. DOCTOR FORMAN SAYS THE MISSION NOW IS TO BETTER UNDERSTAND EFFECTIVE TREATMENT STRATEGIES TO DECREASE OUR WAISTLINES. SINCE EXCESS FAT THERE HAS LONG BEEN LINKED TO HIGHER RISK OF HEALTH

Updated: 11:01 AM CDT Oct 17, 2025

Editorial Standards ⓘ

'Astounding': 70% of adults may be considered obese under new definition of condition

Updated: 11:01 AM CDT Oct 17, 2025

Editorial Standards ⓘ

The prevalence of obesity in adults in the United States could rise sharply under a new definition of the condition released earlier this year by the Lancet Diabetes and Endocrinology Commission, researchers from Mass General Brigham announced Wednesday.When applying the new criteria, which expands upon the traditional use of body mass index (BMI) to include measures of body fat distribution, the prevalence of obesity increased from about 40% to about 70% among more than 300,000 people included in the study. The rise was even more pronounced among older adults, the study found. Additionally, the researchers found that those newly added individuals also had a higher risk of adverse health outcomes. "We already thought we had an obesity epidemic, but this is astounding," said co-first author Dr. Lindsay Fourman, an endocrinologist in the Metabolism Unit in the Endocrinology Division of the Mass General Brigham Department of Medicine. "With potentially 70% of the adult population now considered to have excess fat, we need to better understand what treatment approaches to prioritize."Traditionally, obesity has been defined by BMI, which estimates body fat based on a person’s weight and height. But other anthropomorphic measures — such as waist circumference, waist-to-height ratio, or waist-to-hip ratio — may further account for fat distribution and aid in differentiation between muscle and fat mass.Under the new framework, a person is classified as having obesity if they have a high BMI plus at least one elevated anthropometric measure (a condition the authors term "BMI-plus-anthropometric obesity"), or if they have a normal BMI and at least two elevated anthropometric measures (a condition termed "anthropometric-only obesity"). The new definition also distinguishes between preclinical and clinical obesity, with clinical obesity defined as the presence of obesity-related physical impairment or organ dysfunction. At least 76 organizations have endorsed the new guidelines, including the American Heart Association and The Obesity Society.The study analyzed participants in the National Institutes of Health All of Us Research Program's cohort of more than 300,000 Americans. Obesity prevalence was 68.6% with the new definition, versus 42.9% under the traditional BMI-based definition. This increase was entirely driven by the inclusion of individuals with anthropometric-only obesity. Obesity rates varied by sex, race, and especially by age — affecting nearly 80% of adults over 70.Importantly, the study found that those with anthropometric-only obesity, who would not have been classified as having obesity by the traditional definition, had a higher risk of diabetes, cardiovascular disease and mortality than people without obesity. About half of all individuals who met the new obesity criteria had clinical obesity, and this proportion was only slightly lower in the anthropometric-only obesity group compared with the BMI-plus-anthropometric obesity group."We have always recognized the limitations of BMI as a single marker for obesity because it doesn't take into account body fat distribution," said senior author Dr. Steven Grinspoon, 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 interesting questions about obesity medications and other therapeutics."The researchers emphasize that further studies are needed to better understand the causes of and optimal treatments for anthropometric-only obesity. The research team previously developed a therapeutic that reduces waist circumference and plans to explore the utility of different treatment strategies in this newly defined population."Identifying excess body fat is very important 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."

When applying the new criteria, which expands upon the traditional use of body mass index (BMI) to include measures of body fat distribution, the prevalence of obesity increased from about 40% to about 70% among more than 300,000 people included in the study.

The rise was even more pronounced among older adults, the study found. Additionally, the researchers found that those newly added individuals also had a higher risk of adverse health outcomes.

"We already thought we had an obesity epidemic, but this is astounding," said co-first author Dr. Lindsay Fourman, an endocrinologist in the Metabolism Unit in the Endocrinology Division of the Mass General Brigham Department of Medicine. "With potentially 70% of the adult population now considered to have excess fat, we need to better understand what treatment approaches to prioritize."

Traditionally, obesity has been defined by BMI, which estimates body fat based on a person’s weight and height. But other anthropomorphic measures — such as waist circumference, waist-to-height ratio, or waist-to-hip ratio — may further account for fat distribution and aid in differentiation between muscle and fat mass.

Under the new framework, a person is classified as having obesity if they have a high BMI plus at least one elevated anthropometric measure (a condition the authors term "BMI-plus-anthropometric obesity"), or if they have a normal BMI and at least two elevated anthropometric measures (a condition termed "anthropometric-only obesity").

The new definition also distinguishes between preclinical and clinical obesity, with clinical obesity defined as the presence of obesity-related physical impairment or organ dysfunction.

At least 76 organizations have endorsed the new guidelines, including the American Heart Association and The Obesity Society.

The study analyzed participants in the National Institutes of Health All of Us Research Program's cohort of more than 300,000 Americans.

Obesity prevalence was 68.6% with the new definition, versus 42.9% under the traditional BMI-based definition. This increase was entirely driven by the inclusion of individuals with anthropometric-only obesity. Obesity rates varied by sex, race, and especially by age — affecting nearly 80% of adults over 70.

Importantly, the study found that those with anthropometric-only obesity, who would not have been classified as having obesity by the traditional definition, had a higher risk of diabetes, cardiovascular disease and mortality than people without obesity. About half of all individuals who met the new obesity criteria had clinical obesity, and this proportion was only slightly lower in the anthropometric-only obesity group compared with the BMI-plus-anthropometric obesity group.

"We have always recognized the limitations of BMI as a single marker for obesity because it doesn't take into account body fat distribution," said senior author Dr. Steven Grinspoon, 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 interesting questions about obesity medications and other therapeutics."

The researchers emphasize that further studies are needed to better understand the causes of and optimal treatments for anthropometric-only obesity.

The research team previously developed a therapeutic that reduces waist circumference and plans to explore the utility of different treatment strategies in this newly defined population.

"Identifying excess body fat is very important 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."

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