More Americans may be classified as obese under new definition, study suggests

Researchers at Mass General Brigham have proposed a major update to how obesity is defined, which would classify nearly 70% of U.S. adults as obese, according to a new study published in JAMA Network Open.

With these new criteria, the estimated obesity rate in the U.S. increases from 42.9% to almost 70%, after examining 300,000 people.

The study highlights the limitations of a BMI-based approach, which does not consider how fat stored throughout the body can predict overall health.

Co-first author Lindsay Fourman, M.D., an endocrinologist in the endocrinology division of the Mass General Brigham Department of Medicine, reacted to these findings in a statement.

It is also linked to an increased risk of conditions like diabetes, dyslipidemia, hypertension and cardiovascular disease, he told Fox News Digital.

Redefining obesity to include patients with high-risk fat distribution could help "direct greater clinical attention and resources" to this "vulnerable" group, Rabito suggested.

Dr. Mary Claire Haver, board-certified OBGYN and founder of The 'Pause Life, also said she was not surprised by the study findings.

She added, "From a physiologic and metabolic standpoint, fat distribution matters far more than body weight alone."

"In my patient population, I routinely see individuals who technically meet criteria for obesity based on BMI, but have high lean muscle mass, relatively low visceral fat and excellent metabolic health," she said.

Focusing only on weight can obscure who is "truly at risk," Haver warned, and contributes to stigma while distracting from the "real issue" of metabolic health.

The doctor projected that obesity population numbers will likely improve with the expansion of GLP-1 medications.

"But if we do not shift the conversation away from weight alone and toward body composition and fat distribution, we will continue to misclassify risk and miss opportunities for more personalized, effective care," she added.