Being slightly overweight poses little risk for men and women over 70 - it’s being thinner than normal that can be dangerous, a study found.
Using a formula based on height and weight, researchers found the risk of mortality to be high in underweight adults, rising sharply the leaner they were.
It was not clear why thinness was associated with greater mortality. The researchers excluded from the study older people known to have diseases that would cause them to lose weight.
“For the person 20 pounds overweight, the risk is not there,” said one of the study’s authors, Dr. Steven Heymsfield of St. Luke’s-Roosevelt Hospital in New York. On the other hand, he said, “if you’re underweight and elderly, be concerned. It might be wise to get checked.”
The risks begin to rise for elderly who are 50 to 75 pounds overweight, Heymsfield said.
The findings are particularly important because other studies have shown that many elderly believe they are overweight when they are not, and many moderately overweight elderly are trying to lose weight. This study suggests they may not need to.
Researchers have known for some time that the leanest and the heaviest people at younger ages have the highest risks of mortality. It was not clear whether the same held true in the elderly.
The study by Heymsfield and David Allison shows that it doesn’t; the risks associated with obesity decline except among the extremely obese elderly, who still face an increased mortality risk.
Heymsfield said many moderately overweight elderly might still choose to lose weight even though it would not change their mortality risk.
“I’ve found that some elderly, when they lose weight, feel better,” he said. “It may not increase longevity, but they lose 10 or 20 pounds and they say they can walk around the block, when they couldn’t before.”
Studies have shown that Americans gain weight gradually as they age until about 65, when the population begins to lose weight. The researchers had no clear explanation for this tendency.
Dr. George Bray of the Pennington Biomedical Research Center in Baton Rouge cautioned that studies such as Heymsfield’s can be distorted by the fact that by age 70, the heaviest people might already have died.