For individuals aged 65 and older, the relationship between body weight and long-term health is far more nuanced than a simple number on a scale. While obesity is widely recognized as a risk factor for conditions like heart disease and type 2 diabetes, new research indicates that relying solely on Body Mass Index (BMI) can be misleading for the aging population.
The study, which analyzed data from nearly 7,000 adults aged 65 and older, tracked participants for up to 14 years. The findings revealed a complex picture: while being classified as overweight by BMI was actually associated with a lower risk of early death, the same did not hold true for waist circumference. Men with a waist measurement exceeding 40 inches (101.6 centimeters) and women with one over 35 inches (89 centimeters) faced a 24% higher risk of early mortality compared to those below these thresholds. This increased risk persisted even after researchers adjusted for BMI.
Dr. Leana Wen, an emergency physician and clinical associate professor at George Washington University, notes that these findings should not be interpreted as evidence that excess body fat is protective. Instead, the results highlight the limitations of BMI as a health metric in older age. BMI is calculated using only height and weight, failing to distinguish between muscle mass and body fat. As people age, they naturally tend to lose muscle mass, meaning a person with a “normal” BMI might actually have dangerously low muscle levels and high body fat, while someone with a higher BMI might have better muscle preservation.
The study also observed an “obesity paradox,” where individuals in certain overweight or obese BMI categories appeared to have a lower risk of death. Dr. Wen explains that this is likely due to reverse causation and survivorship bias. For instance, individuals may lose weight due to underlying illnesses like cancer or heart disease, making lower weight appear linked to higher mortality. Furthermore, those who reach older age despite having obesity may possess different physiological characteristics than those who succumbed to obesity-related diseases earlier in life.
Conversely, the study found that underweight older adults faced nearly double the risk of early death compared to those in the normal BMI range. This vulnerability is often tied to frailty, as older adults require sufficient muscle strength to maintain mobility and prevent falls. When weight loss is driven by muscle depletion, it leaves individuals more susceptible to health complications, regardless of whether their BMI is moving toward a conventionally “healthier” range.
To better assess health risks, experts suggest that waist circumference is a more effective proxy for visceral fat—the “hidden” fat stored deep within the abdomen around internal organs. This type of fat is strongly linked to inflammation, insulin resistance, and metabolic changes that drive cardiovascular disease. Unlike BMI, measuring waist circumference is a simple, non-invasive process that can be performed at home using a tape measure placed between the bottom of the ribs and the top of the hip bones.
Ultimately, medical professionals recommend that patients consider waist measurements alongside other vital health indicators, such as blood pressure, cholesterol levels, blood sugar, and overall physical fitness. By moving beyond the limitations of BMI, older adults and their doctors can gain a more accurate understanding of body composition and its impact on longevity. 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 leana Wen: The researchers analyzed data from nearly 7,000 adults ages 65 and older who were followed as part of a large and nationally representative study funded by the US National Institutes of Health. The report also notes that men who were overweight, defined as a BMI between 25 and 29.9, had a 46% lower risk of death, compared with men whose BMI was in the normal range. The report also notes that defined as a BMI between 30 and just under 40, also had a lower risk, those with class I or II obesity. The report also notes that among women, those who were overweight had a 27% lower risk of death than those in the normal BMI range.