Does waist size predict death better than BMI after 65?
Yes. In 6,905 US adults aged 65 and older, a high waist size came with about 24% higher risk of dying (hazard ratio 1.24), while men in the “overweight” BMI category had about 46% lower risk than men at a normal weight. Waist size pointed at real risk. BMI pointed the wrong way.
Body mass index is just weight compared to height. It cannot tell muscle from fat, and it cannot tell where the fat sits. Waist circumference is a tape measure around the middle, and it captures the fat packed around the organs in the belly. In older people those two numbers can tell completely opposite stories, and this study shows how far apart they can get.
What the data show
Researchers followed participants in the National Health and Aging Trends Study for 14 years, from 2011 to 2024, and tracked who died. Compared with normal weight men, men in the overweight category had about 46% lower risk of death (hazard ratio 0.54), very likely somewhere between 34% and 55% lower (95% confidence interval 0.45 to 0.66). Men with class I or class II obesity did not fare worse either. Their risk was about 51% lower (hazard ratio 0.49), very likely between 35% and 63% lower (0.37 to 0.65).
Waist size ran the other way. In men, a high waist came with about 24% higher risk of death (hazard ratio 1.24), very likely between 7% and 44% higher (1.07 to 1.44). The authors report similar patterns in women. When the two measures were looked at together, the group that stands out is people carrying a normal BMI with a high waist. That combination came with higher death risk in both sexes. Being underweight also raised risk, no matter what the waist measured.
Dr. Kumar’s Take
The headline here is not “carrying extra weight is good for you.” It is that BMI stops working as a risk tool once people get older, and the tape measure keeps working. Someone can sit in the “normal” BMI range and still carry a high waist. On paper that person looks fine. This study says that person is the one at higher risk.
There is a second explanation worth holding onto. Older adults lose weight when they are sick, so serious illness pushes people into the lower BMI categories before it kills them. That alone can make higher BMI look protective in this kind of data. This was an observational study, so it can show which measurements travel with death risk, not that changing a number changes the outcome.
Why the middle matters more than the scale
Fat stored around the abdominal organs behaves differently from fat under the skin on the hips and thighs. It is metabolically active, it feeds inflammation, and it tracks with insulin resistance. That is the biology behind why a waist measurement adds information the scale cannot supply. In older adults there is a second layer: a stable weight can hide muscle being swapped out for fat over the years. The scale does not move, the risk does.
Limits worth knowing
These are associations from one long running US cohort, and the models adjusted for baseline age, race, education, annual income, smoking status, and homebound status. Other factors, including illness that was already present, can still shape results like these. The study enrolled adults 65 and older, so the findings describe that age group and should not be carried over to younger people. The study also does not tell us whether shrinking a waist later in life lowers risk, only that a larger waist marks higher risk.
Practical Takeaways
- Measure your waist with a tape at the level of the navel, standing and relaxed, and track that number over time along with your weight.
- If your BMI is in the normal range but your waist has grown over the years, treat that as a real risk signal rather than a clean bill of health.
- In older adults, unplanned weight loss deserves a medical workup rather than congratulations, since being underweight carried higher death risk in this study.
- Focus on keeping muscle through resistance training and adequate protein, since preserving muscle changes body composition in a way the scale alone will never show.
Related Studies and Research
- Long daytime naps linked to higher death risk in older adults
- The high-dose flu shot may lower Alzheimer’s risk in older adults
- PPIs cause low magnesium: meta-analysis reveals 43% higher risk
- Irregular sleep in surgeons linked to higher patient risk
FAQs
What counts as a high waist circumference?
Start with how you take the measurement, because a waist recorded differently each time cannot be compared. Measure over bare skin or a thin layer, at the end of a normal breath out, without pulling the tape tight enough to press into the skin. Doing it the same way each time matters more than getting a perfect single reading, because you are watching the trend. A waist that has grown two inches over five years is meaningful even if it has not crossed a cutoff.
Should older adults try to lose weight?
This study cannot answer that, because it measured body size and death, not the effect of a weight loss plan. What it does show is that after 65 a higher BMI tracked with lower death risk while a high waist tracked with higher risk, so the scale is not the number that flagged danger here. Losing waist size while holding onto muscle is a different project from losing weight, and it calls for resistance training and enough protein alongside any diet change. Any deliberate weight loss late in life is worth planning with a physician who knows your history.
Why does BMI look protective in older adults?
Part of it is that BMI cannot separate muscle from fat, so an older person with more muscle and a bit of reserve lands in the overweight category and does well. Part of it is reverse causation: illnesses like cancer, heart failure, and dementia strip weight off people in the months and years before death, which loads the lower BMI groups with sick people. Researchers try to adjust for this, but no adjustment fully removes it from observational data. That is exactly why a measure of where the fat sits, rather than how much a person weighs, holds up better in this age group.
Bottom Line
Across 14 years and 6,905 older Americans, BMI and waist size disagreed, and waist size was the one that tracked real risk. A high waist came with about 24% higher death risk, while overweight and moderate obesity by BMI came with lower risk in men, with similar patterns in women. The group most likely to be reassured by a routine checkup, someone with a normal BMI and a growing waist, was the one carrying elevated risk. If you are over 65, the tape measure tells you more than the scale.
