Higher BMI Linked to Lower Death Risk in Seniors, but Waist Size Tells a Different Story

A study by researchers at the University of Rhode Island found that a higher body mass index (BMI) among US adults over 65 was linked with a lower risk of death, while a larger waist circumference -- a sign of excess abdominal fat -- was independently associated with higher mortality once BMI was accounted for. The study, published in the Journal of the American Geriatrics Society, analyzed 14 years of data from 6,905 participants in the National Health and Aging Trends Study.

Men with class I or "low risk" obesity had a 46% lower risk of all-cause mortality compared with those in the normal BMI category, and men with class II obesity had a 51% lower risk. In contrast, men with a waist circumference above 40 inches (102 cm) had a 24% higher mortality risk; the equivalent large-waist threshold for women in the study was 35 inches (89 cm).

"Our findings suggest that considering both measures together, rather than relying on BMI alone, may improve mortality risk assessment and support more informed clinical decision-making," said study co-author Bryan Blissmer. The findings add to a body of evidence around the "obesity paradox," in which a BMI between 25 and 35 has, in various studies, been linked with a survival advantage among older adults, even though obesity is separately linked with heart disease, type 2 diabetes and other chronic conditions.

The study was observational and its measurements were self-reported, and the researchers noted it cannot determine whether fat distribution or overall body fat is the more important factor. Natalie Shilton of Griffith University in Australia, who was not involved in the study, said the results suggest abdominal obesity is linked with higher mortality risk "even in individuals whose weight is considered within a normal range." Garron Dodd of the University of Melbourne, also not involved in the study, said BMI cannot distinguish fat from muscle, and that after 60, a low BMI often reflects lost muscle rather than leanness.