A waist tape measure may tell doctors more about an older adult's risk of dying than a bathroom scale or a BMI chart, according to a study published in the Journal of the American Geriatrics Society that tracked nearly 7,000 Americans for more than a decade.
Researchers led by Bryan Blissmer of the University of Rhode Island followed 6,905 U.S. adults aged 65 and older from 2011 to 2024, drawing on nationally representative health survey data to see how body mass index and waist circumference, tracked over time rather than at a single checkup, related to death from any cause. Men with a waist circumference above 40 inches (101.6 centimeters) and women above 35 inches (89 centimeters) — thresholds already used clinically to flag abdominal obesity — had a 24 percent higher risk of dying during the study period than those below those marks, even after accounting for BMI.
The study also surfaced a pattern that has puzzled geriatric researchers for years: among men, being in the overweight BMI range was linked to a 46 percent lower risk of death, and class I-II obesity to a 51 percent lower risk, compared with normal-weight men. Being underweight, by contrast, carried a consistently higher death risk in both sexes regardless of waist size. "BMI and waist circumference provide complementary information about health risk in older adults," Blissmer said, arguing the two measurements answer different questions rather than one simply correcting the other.
The apparent survival edge for higher BMI in older age — sometimes called the "obesity paradox" — has been reported in prior aging research and is generally not read as evidence that carrying extra weight is protective. Muscle and bone naturally decline with age, so an older adult's weight increasingly reflects a mix of fat, frailty and lean mass that BMI alone cannot distinguish. Physicians who study the issue have cautioned that someone who has lost muscle to illness or inactivity can register a "healthy" BMI while still carrying dangerous levels of abdominal fat, a combination sometimes described informally as "skinny fat," which the waist measurement is better positioned to catch.
Abdominal fat, particularly the visceral fat that accumulates around internal organs, is more metabolically active than fat stored elsewhere on the body and has been linked in other research to higher rates of heart disease, type 2 diabetes and inflammation — plausible mechanisms for why waist size tracked mortality independently of overall weight in the new analysis. The authors note their data are observational, meaning the study can show an association between body measurements and death but cannot prove that abdominal fat itself causes earlier death, and the sample was drawn entirely from U.S. adults, leaving open how well the specific thresholds apply elsewhere.
The findings add to a broader push within geriatric medicine to move away from BMI as a stand-alone screening tool, especially for patients over 65. The authors suggest clinicians treat waist circumference as a routine companion measurement to BMI during checkups rather than an optional add-on, particularly since a simple tape measure requires no special equipment. Further research, including studies that track how waist size changes alongside strength and mobility over time, is expected to test whether adding routine waist measurements to geriatric checkups changes health outcomes rather than just flagging risk after the fact.
