Researchers actually have a name for this: the obesity paradox. Adults over 65 with a BMI in the 25-27 range — "overweight" by the standard chart — repeatedly show better health outcomes and lower mortality than same-age adults sitting in the supposedly "healthy" 18.5-24.9 band. It's counterintuitive enough that it took a body of published research, not just a stray observation, before it became a widely recognized pattern in geriatric medicine.
Why the standard scale gets applied more cautiously past 65
The familiar adult BMI categories — under 18.5 underweight, 18.5-24.9 healthy, 25-29.9 overweight, 30+ obesity range — were built mostly from working-age population data. Multiple systematic reviews of older populations have consistently found the opposite pattern from what those categories assume: mildly overweight adults over 65, sometimes even those in the lower obesity range, often outlive same-age peers sitting in the "healthy" band. Some research suggests the actual optimal range may run even a bit higher, closer to 27-30, and that women's optimal range may sit 2-5 points higher than men's — a level of nuance the flat adult categories were never built to capture.
What's likely behind the pattern
A few factors show up repeatedly in the research:
- Muscle loss (sarcopenia): older adults naturally lose muscle over time, so a slightly higher body weight can reflect a genuine energy and nutritional reserve rather than excess fat
- Frailty risk: being underweight, or losing weight unintentionally later in life, is tied to greater frailty, higher fall risk, and worse recovery from illness or surgery
- Chronic illness: unplanned weight loss can be an early warning sign of underlying illness, which is part of why a low BMI carries more concern in this age group than a moderately elevated one does
What this actually changes in practice
For adults over 65, an unplanned drop in weight or BMI is often the more significant signal to watch for — more so than sitting in the "overweight" range — particularly when that drop happens without any deliberate change in diet or activity. That's a real inversion of how BMI concerns typically get framed for younger adults.
BMI still has the same blind spots at any age
BMI still can't tell muscle from fat, at 25 or 85, and it says nothing about where fat sits on the body, which matters independently for cardiovascular risk. For older adults specifically, tracking the trend over time — rather than fixating on a single reading against the standard chart — alongside broader markers like mobility, strength, and appetite, tends to tell a more complete story than a BMI category alone ever could.
Checking your own number
Use the BMI Calculator to see where you currently fall, and talk through what that number actually means for you with a healthcare provider — especially past 65, since the standard categories genuinely get applied with more nuance in this age group than the general population framing suggests.
A few things people actually ask
What is the "obesity paradox"?
The well-documented finding that mildly overweight and sometimes mildly obese older adults show lower mortality risk than same-age adults in the "healthy" BMI range — the opposite pattern from what's typically assumed for younger adults.
Should I be more worried about weight loss than weight gain after 65?
Research suggests unplanned weight loss is often the more significant signal to watch for in this age group, particularly when it happens without any deliberate change in diet or activity — this is a genuine shift from how BMI concerns are typically framed for younger adults, though any specific concern should be discussed with a healthcare provider.
Does the optimal BMI range differ between men and women in later life?
Some research suggests women's optimal range may sit a few points higher than men's, though individual health circumstances matter more than any general pattern.