Mass General Brigham recommends change in how we look at obesity
Mass General Brigham
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The study examined data from more than 300,000 people and found
that the increase was especially pronounced among older adults. The findings
also showed that many individuals newly classified under the updated definition
face higher risks of serious health problems. The study was published in JAMA
Network Open.
"We already thought we had an obesity epidemic, but
this is astounding," said co-first author Lindsay Fourman, MD, an
endocrinologist in the Metabolism Unit in the Endocrinology Division of the
Mass General Brigham Department of Medicine. "With potentially 70 percent
of the adult population now considered to have excess fat, we need to better
understand what treatment approaches to prioritize."
Why BMI Alone May Miss Health Risks
For decades, obesity has primarily been defined using body
mass index (BMI), a calculation based on height and weight. While BMI offers a
simple estimate, it does not capture how fat is distributed throughout the
body. Other anthropomorphic measures -- including waist circumference,
waist-to-height ratio, and waist-to-hip ratio -- can provide additional insight
by distinguishing fat mass from muscle and identifying abdominal fat linked to
disease risk.
Under the updated framework, obesity is identified in two main ways. Individuals with a high BMI plus at least one elevated anthropometric measure are classified as having obesity, a category the authors call "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 participants from the National
Institutes of Health All of Us Research Program, which includes more than
300,000 Americans. 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 would not have been labeled as having obesity 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 because 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 interesting 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
may 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 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."
Authorship: In addition to Fourman and Grinspoon, Mass
General Brigham authors include Aya Awwad, Camille A. Dash, Julia E. Johnson,
Allison K. Thistle, Nikhita Chahal, Sara L. Stockman, Mabel Toribio, Chika
Anekwe, and Arijeet K. Gattu. Additional authors include Alba
Gutiérrez-Sacristán.
Disclosures: Fourman serves as a consultant to
Theratechnologies and Chiesi Farmaceutici and receives grant funding to her
institution from Chiesi Farmaceutici outside of this work. Grinspoon serves as
a consultant to Marathon Assets Management and Exavir Therapeutics and receives
grant funding to his institution from Kowa Pharmaceuticals, Gilead Sciences,
and Viiv Healthcare, unrelated to this project. For the remaining authors, no
conflicts were declared.
Funding: This work was supported by the National
Institutes of Health (grants K23HD100266, 1R01AG087809, T32DK007028,
K23HL147799, 1R01HL173028, and P30DK040561) as well as the American Heart
Association-Harold Amos Medical Research Faculty Development Program, supported
by the Robert Wood Johnson Foundation, and the Robert A. Winn Excellence in
Clinical Trials Award Program from the Bristol Meyers Squibb Foundation. The
funding organizations played no role in the design and conduct of the study,
collection, management, analysis, and interpretation of the data; preparation,
review, or approval of the manuscript; and decision to submit the manuscript
for publication.
