KINGSTON, R.I. – Sept. 10, 2026 – A longitudinal study led by University of Rhode Island researchers found that waist circumference and body mass index (BMI) provide distinct and complementary information about mortality risk among older adults. Previous studies examining BMI among older adults have produced seemingly conflicting findings regarding mortality risk.
This study used data collected from 2011-2024 from 6,905 adults aged 65 or older who participated in the National Health and Aging Trends Study. By considering repeated measurements of BMI and waist circumference together, the researchers developed a fuller picture of their associations with mortality. The study was published online in the Journal of the American Geriatrics Society in August.
The multidisciplinary research team included lead author Furong Xu, professor of health and physical education, URI Feinstein College of Education; Jacob Earp, assistant professor and research associate of kinesiology, University of Connecticut; Bryan Blissmer, professor of kinesiology, URI College of Health Sciences; Julie Coiro, professor of literacy education, URI Feinstein College of Education; Steven Cohen, associate professor of public health, URI College of Health Sciences; and Geoffrey Greene, professor of nutrition, URI College of Health Sciences.
Blissmer answered questions about the study on behalf of the team.
Why was this topic selected?
We were interested in a question that sounds straightforward, but becomes more complicated as we age: What does body weight tell us about health? Older adults can lose muscle and accumulate more fat around their middle without much change on the scale. That makes weight alone difficult to interpret.
There has also been a longstanding debate about why older adults classified as overweight sometimes have better survival than those in the “normal” BMI range. We wanted to examine that more closely by considering overall body size and waist circumference together, using repeated measurements as people aged.
Did studying waist size with BMI more accurately predict mortality?
BMI tells us how someone’s weight relates to their height, but it cannot distinguish muscle from fat or tell us where fat is located. Waist circumference adds information about abdominal fat, but it cannot tell us how much muscle someone has nor provide a complete picture of their nutritional status. Each measurement gives us information the other misses.
Our findings support considering the two together for a fuller understanding of mortality risk. One distinction though is this study examined deaths, not the development of illnesses, and it did not formally test whether a combined prediction tool was more accurate.
What patterns or surprises emerged from the research?
In models examining BMI independently, being overweight was associated with lower mortality in both sexes. In separate models accounting for BMI, a high waist circumference was associated with approximately 24% higher mortality in both men and women. Being underweight was also associated with substantially higher mortality.
What stood out was that people with a “normal” BMI, but a high waist circumference had higher mortality than those with a normal BMI and a smaller waist. That challenges the assumption that a normal BMI necessarily means low risk. The contrasting information from the two measurements was more informative than the finding about overweight alone.
What should people take away from this study?
The number on the scale is only part of the story. BMI should not be used in isolation when assessing obesity-related health risks. While BMI can still be useful, but it should be interpreted alongside waist circumference, changes in weight, strength, physical function, and overall health.
We would not want someone to read this as a reason to gain weight or assume that extra body fat is protective. We observed associations; we did not establish that gaining weight helps people live longer. For older adults, maintaining muscle, mobility, and good nutrition deserves attention alongside body weight and unexplained weight loss should not automatically be viewed as a positive.
Is more research related to this topic planned?
Yes. We are continuing this work by examining whether patterns of change in BMI and waist circumference may help identify thresholds associated with mortality and whether those patterns relate to outcomes such as physical function, frailty, and healthy aging. Those analyses are still developing. Ultimately, we want to understand both how long people live and how well they maintain their independence and quality of life.