A recent cohort study of 6,905 people aged 65 years and older (data collected 2011–2024) examined how body mass index (BMI) and waist circumference relate to all-cause mortality. The study, published in the Journal of the American Geriatrics Society, found divergent associations for BMI versus waist size.
Among men over 65, an overweight BMI was associated with a 46% reduction in the risk of all-cause mortality compared with people classified as healthy weight or underweight. Men with class I or class II obesity showed an associated 51% lower risk. By contrast, a high waist circumference predicted increased mortality: in men, a large waist was associated with a 24% higher risk of all-cause death compared with those with a healthier waist measurement. The study reported a similar adverse effect of high waist circumference in women, although the BMI–mortality relationships differed by sex.
Authors and quoted experts framed these findings in light of the so-called "obesity paradox" in older adults: higher BMI in later life may sometimes correlate with lower observed mortality, potentially because BMI does not distinguish fat distribution, muscle mass, or bone density. The study data suggest that BMI and waist circumference capture different aspects of risk in older adults.
The study also identified elevated mortality risk among individuals with an underweight BMI. Experts quoted in the source interpreted some of the protective association between higher BMI and survival as likely reflecting lower frailty and the absence of severe chronic or terminal illnesses that often cause weight loss. Jayne Morgan, MD, noted that "In [older adults], some weight may actually be protective," and suggested greater weight can indicate "less frailty, less debilitating illness, and lack of terminal illnesses that often portend severe weight loss."
Because aging is often accompanied by loss of muscle mass and bone mineral density, BMI can decline even while underlying health is worsening. Thus, a low BMI in an older person may be a marker of poor health rather than a marker of lower adiposity. The study therefore highlights that being underweight, regardless of waist circumference, "portends the highest mortality risk," a point emphasized by Morgan.
The association between larger waist circumference and greater all-cause mortality is less surprising and aligns with known cardiometabolic mechanisms. A higher waistline often reflects increased visceral or truncal fat—fat stored around internal organs such as the kidneys, liver, heart, pancreas, and digestive organs—which carries metabolic consequences.
Clinicians quoted in the article warned that increases in waist size are particularly concerning in perimenopausal and menopausal women, where a 2–3 inch increase in waist circumference may signal greater cardiometabolic risk. Jayne Morgan highlighted that a larger waist raises the likelihood of increased insulin resistance, unfavorable cholesterol changes, a pro-inflammatory state, and increased risks of heart attack and stroke.
The article reported standard waist circumference thresholds from NHLBI guidance: a high waistline is defined as 40 inches or more in men and 35 inches or more in women. The study found that a normal BMI combined with a high waist circumference was associated with higher mortality in both sexes, underscoring the independent prognostic value of waist measurement.
The study’s sex-specific findings underscore limitations of BMI as a universal health metric. In this cohort, class I and class II obesity did not confer a significant mortality advantage in females, although the overweight category did. Experts pointed out how BMI can misclassify body composition and fat distribution, particularly in women.
The article describes the so-called "skinny fat" phenotype in women: individuals with a normal BMI but central fat redistribution who carry excess visceral fat and therefore a higher metabolic and cardiovascular risk, yet who may be labeled as "normal weight" by BMI alone. This pattern illustrates why waist circumference can uncover risk not apparent from BMI.
The source also raised equity concerns: Morgan noted that BMI-based criteria—such as some heart-transplant BMI guidelines—can disadvantage groups that typically carry weight in a healthier distribution (for example, people who are "pear-shaped" with weight in hips and thighs rather than the torso). The article asserted that using BMI alone can lead to clinically consequential misclassification.
The study used a cohort of 6,905 individuals aged 65+ over the period 2011–2024 and was published in the Journal of the American Geriatrics Society. Reported key quantitative findings from the source include a 46% lower all-cause mortality risk for overweight men and a 51% lower risk for men with class I and II obesity, while high waist circumference carried an approximately 24% higher mortality risk in men and a similar effect in women. The article emphasized that BMI cannot measure true body fat or overall health and that waist circumference more directly signals harmful visceral adiposity.
The source did not provide detailed clinical recommendations beyond expert commentary. It cautioned against relying on BMI alone for assessing health in older adults and highlighted the prognostic importance of measuring waist circumference alongside BMI when evaluating cardiometabolic risk and overall mortality risk in people aged 65 and older.
Details on management strategies or guideline changes were not reported in the source article.