For adults aged 65 and older, the relationship between body weight and longevity is more nuanced than a simple number on a scale. A recent study involving nearly 7,000 participants, funded by the US National Institutes of Health, indicates that while traditional body mass index (BMI) metrics often suggest an “obesity paradox,” waist circumference serves as a more reliable indicator of early death risk.
Researchers tracked participants for up to 14 years to evaluate how fluctuations in BMI and waist measurements correlated with mortality. The findings revealed that men classified as overweight—with a BMI between 25 and 29.9—had a 46% lower risk of death compared to those in the normal BMI range. Similarly, men in the class I or II obesity categories, defined as a BMI between 30 and 39.9, also showed a reduced risk. Among women, those classified as overweight experienced a 27% lower risk of mortality than their counterparts in the normal range. However, for both genders, class III obesity (a BMI of 40 or higher) showed no statistically significant difference in mortality risk.
The data shifted significantly when researchers analyzed waist circumference. Individuals with larger waistlines—exceeding 40 inches for men and 35 inches for women—faced a 24% higher risk of early death compared to those below these thresholds. This elevated risk persisted even after adjusting for BMI, suggesting that where fat is stored matters more than total body weight in older populations.
Dr. Leana Wen, an emergency physician and clinical associate professor at George Washington University, notes that these findings do not imply that gaining body fat is protective. Instead, the “obesity paradox” likely stems from factors such as reverse causation, where underlying illnesses like cancer or heart disease cause weight loss, or survivorship bias, where individuals who reach older age despite obesity differ from those who succumbed to weight-related conditions earlier. Furthermore, BMI is an inherently limited tool because it fails to distinguish between muscle mass and body fat.
As people age, they naturally lose muscle mass and experience changes in fat distribution. A person with a “normal” BMI might actually have lost significant muscle while retaining excess fat, while someone with a higher BMI might possess more lean muscle. Because BMI cannot capture these body composition shifts, it becomes a less effective health gauge for seniors.
Visceral fat, which accumulates deep within the abdomen around internal organs, is strongly linked to inflammation, insulin resistance, and metabolic issues that drive diabetes and cardiovascular disease. Measuring waist circumference is a straightforward, non-invasive method to estimate this hidden fat. Experts recommend that patients and physicians use waist measurements alongside BMI, blood pressure, cholesterol, and blood sugar levels to form a comprehensive health profile.
To measure correctly at home, one should place a tape measure around the abdomen between the bottom of the ribs and the top of the hip bones, ensuring the tape is level and snug without compressing the skin. The study also highlighted that being underweight is associated with a nearly doubled risk of early death compared to those in the normal BMI range. This is largely attributed to frailty, as older adults require muscle strength to maintain mobility, perform daily tasks, and prevent dangerous falls. Losing weight due to muscle atrophy can leave an individual more vulnerable, even if their BMI shifts toward a range typically labeled as healthier. The report also notes that obesity, we know, is associated with increased risks of many conditions, including heart disease and type 2 diabetes. The report also notes that to learn what this research means for healthy aging, I spoke with wellness expert Dr. The report also notes that she previously served as Baltimore’s health commissioner. The report also notes that men with a waist circumference greater than 40 inches (101.6 centimeters) and women with one greater than 35 inches (89 centimeters) had a 24% higher risk of early death compared with those below those thresholds. The report also notes that and the authors explicitly caution that their findings should not be interpreted as evidence that excess body fat is biologically protective, it does not establish that gaining body fat will help people live longer. The report also notes that consider two people of the same height and weight.
