More Americans could be classified as obese under a proposed new definition

Researchers at Mass General Brigham proposed adding waist and body‑fat measures to BMI; applying their criteria to about 300,000 adults raised the estimated U.S. obesity rate from 42.9% to nearly 70%, and nearly 80% of participants over 70 met the new threshold.

Researchers at Mass General Brigham published a study in JAMA Network Open proposing an update to how obesity is defined. The proposed benchmark adds waist circumference and body fat location to the commonly used BMI measure. The study applied the new criteria to roughly 300,000 adults and reported a large increase in the portion of people meeting an obesity definition. Older adults showed the largest rise under the new criteria. Key findings: - The proposed definition supplements BMI with waist and body‑fat measurements and identifies fat distribution rather than only overall weight. - Applying the new criteria to the study sample increased the estimated adult obesity rate from 42.9% to nearly 70%. - The increase was largest among participants over 70 years old, where nearly 80% met the new obesity threshold. - Study authors and clinicians cited limits of BMI alone and noted visceral (abdominal) fat is linked to higher risks for conditions such as diabetes and cardiovascular disease, and that redefining obesity could change which patients receive clinical attention or therapies. Summary: The proposed definition would broaden the group labeled obese by emphasizing body‑fat distribution in addition to weight. Undetermined at this time.