New research indicates that adults aged 65 and older with a larger waist circumference may face a higher risk of dying prematurely. Interestingly, those categorized as overweight based on body mass index (BMI) appeared to have a reduced risk of early death.
This finding is, well, a bit perplexing.
While we know that obesity is linked to greater risks for various health issues, such as heart disease and type 2 diabetes, the dynamics between body weight and health in older adults seem to be more nuanced than just a simple number on the scale.
So, how can older individuals and their healthcare providers interpret these seemingly contradictory results from a study published on August 19 in the Journal of the American Geriatrics Society?
To shed light on this, I connected with Dr. Leana Wen, a wellness expert from CNN. Wen is not only an emergency physician but also a clinical associate professor at George Washington University and has previously served as Baltimore’s health commissioner.
CNN: What did the study reveal about BMI, waist circumference, and longevity in older adults?
Dr. Leana Wen: The study looked at data from nearly 7,000 adults aged 65 and older, part of a large, representative study funded by the US National Institutes of Health. Participants were monitored for up to 14 years to see how changes in BMI and waist circumference related to mortality risk.
For instance, compared to men with a normal BMI, those defined as overweight—having a BMI between 25 and 29.9—had a 46% lower risk of death. This trend continued for those classified as having class I or II obesity, with a BMI between 30 and just under 40.
Among women, overweight individuals had a 27% lower risk of death than their normal BMI counterparts. However, class I and II obesity did not show a significant difference in mortality risk. Additionally, both men and women with class III obesity, defined as a BMI of 40 or more, showed no notable difference in death risk.
When evaluating waist circumference, the findings diverged significantly. Men with a waist circumference exceeding 40 inches and women surpassing 35 inches had a 24% higher risk of early death compared to those below those measurements. Notably, this increased risk persisted even after controlling for BMI.
CNN: Does this mean being overweight or having more body fat might be beneficial as one ages?
Wen: Not exactly. While the study discovered a link between certain BMI categories and reduced mortality, it does not prove that gaining body fat equates to longer life. The authors of the study caution against interpreting their findings as suggesting that excess body fat is somehow protective.
There are several theories attempting to explain what’s sometimes referred to as the “obesity paradox.” How can obesity increase the risk of serious medical conditions while simultaneously being linked to lower mortality among some older adults?
One potential reason is reverse causation, where weight loss occurs due to illnesses like cancer or heart disease. This scenario could lead to the misinterpretation of a lower weight as being associated with greater mortality risk, as underlying health issues may be affecting both. Additionally, survivorship bias plays a role—older individuals who have obesity but reach advanced age may differ significantly from those who succumb to obesity-related illnesses earlier.
CNN: Why might BMI be less effective in gauging health as people get older?
Wen: BMI is a measure based purely on height and weight. While it serves as a useful tool for assessing trends in large populations, it doesn’t reveal the composition of an individual’s weight.
For example, two people of the same height and weight could have drastically different body compositions—one may have significant muscle mass, while the other could be higher in fat. Yet, they could share the same BMI.
This distinction becomes even more pronounced with aging, as people typically lose muscle mass. Older adults may also shrink in height and experience changes in fat distribution. Thus, a higher BMI in an older individual might indicate maintained lean mass, while someone with a normal BMI could be losing muscle and harboring excess body fat.
CNN: What makes waist fat different? Should individuals measure waist circumference in conjunction with knowing their BMI?
Wen: Visceral fat, often termed “hidden fat,” accumulates around internal organs in the abdomen and is associated with inflammation, insulin resistance, and other metabolic shifts that elevate risks for cardiovascular disease and diabetes.
Measuring waist circumference provides a straightforward way to estimate visceral fat. Many healthcare experts advocate for employing measures of body fat, like waist circumference, alongside BMI to better assess obesity.
It’s relatively easy to measure waist circumference at home without the need for specialized equipment. By placing a tape measure snugly around the abdomen, between the base of the ribs and the top of the hipbones, patients can monitor this simple metric. This can be discussed with their healthcare provider along with BMI and other health indicators like blood pressure and cholesterol levels.
CNN: The study also highlighted increased mortality risk among underweight older adults. What could explain this?
Wen: Yes, indeed. The study found that men and women who were underweight faced nearly double the risk of early death compared to those with a normal BMI. This is understandable, as low weight can lead to frailty. Muscle strength is vital for older adults to carry out daily tasks, maintain mobility, and lower fall risk. If someone is losing weight due to muscle loss, they could be more susceptible to health issues—even if their BMI edges closer to what is conventionally viewed as a healthy range.
However, we must tread carefully in interpreting this relationship. Being underweight may arise as a consequence rather than a cause of health problems. Chronic illnesses can lead to unintended weight loss and muscle degradation, and such loss is often a sign of an underlying medical issue.
CNN: If monitoring BMI isn’t sufficient, what should older adults prioritize to manage their health?
Wen: I recommend that older adults place far greater emphasis on their overall health and functional ability rather than fixating on a specific weight number. Can you stay active? Can you handle daily activities unaided? It’s crucial to maintain muscle strength. Therefore, setting physical activity goals and prioritizing exercises—including both aerobic activities and strength training—should be at the forefront. Proper nutrition, particularly ensuring adequate protein intake, is equally important.
It’s essential to be mindful of changes over time. An increase in waist circumference might indicate rising abdominal fat, even if weight and BMI stay relatively stable. On the flip side, unexpected weight loss should prompt a discussion with a healthcare professional. It’s wise to consult your doctor about what constitutes a healthy weight for you, considering factors beyond just the scale, such as body composition, fat distribution, and other health metrics, including blood pressure and blood sugar levels.
