|
|
|
 |
Older men don't burn as many calories after overeating as their
younger counterparts, so they may have to compensate by doing
a little more exercise--such as taking a walk after dinner. Earlier
studies have implied that aging hampered the body's ability to
increase its resting metabolic rate--the energy needed to keep
the resting body functioning--and thus "waste" the extra
calories. So researchers tested the thesis by feeding a small
group of men in their 60s and 70s and another group in their 20s
an extra 1,000 calories a day for three weeks. Both age groups
had an increase in metabolic rate, but the older group had a smaller
increase, the researchers reported in the Journal of Gerontology.
The difference amounted to about 87 calories a day that the older
group would store as fat if they didn't increase their exercise.
That adds up to an extra 2.2 pounds per year or 22 pounds a decade,
the researchers estimate. On any given day, people may fluctuate
between eating 500 to 1,000 calories more or less than needed.
So the men's ability to "save" calories in times of
scarcity was also tested by giving them 750 calories less than
needed to maintain weight for three weeks. In this case, both
groups decreased their metabolic rate about the same. Earlier,
the researchers reported that the young group automatically reduced
their calorie intake after the overeating period, whereas the
older group continued to overeat. Taken together, the findings
help explain why body fat creeps up in older men.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts,
Boston, MA
Susan Roberts/Paul Fuss, (617) 556-3237
A genetic variation that may increase the risk of osteoporosis
can be counteracted by raising calcium intake, according to a
study of 60 women. When the intake was 1,500 milligrams a day,
the 26 women who had the genetic variant absorbed just as much
calcium as the 34 women with a normal gene. But when calcium intake
was reduced to less than 300 mg/day, those with the variant absorbed
significantly less. That's because intestinal cells have to actively
pump in the calcium when the supply is scarce rather than letting
it seep in when there's plenty. And active absorption requires
vitamin D and a functional vitamin D receptor--a molecule that
sits at the surface of cells and hooks up with the vitamin to
activate the process. The "osteoporosis gene," discovered
in 1994 by an Australian scientist, is a variation of the vitamin
D receptor gene, which apparently renders the vitamin D receptor
less efficient. The findings are consistent with earlier results
in this laboratory showing that the association between the "osteoporosis
gene" and hip bone loss depended on the calcium intake level.
And it may explain why some studies have seen a relationship between
the genetic variation and bone mineral density while others have
not.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts,
Boston, MA
Bess Dawson-Hughes, (617) 556-3064
For more information visit ARS
Nutrition Briefs
Last updated: July 10, 1996
Return to: Quarterly
Report Table of Contents
|
|
|
|
|
Last Modified: 02/11/2002
|
|
Printable Version
E-mail this page
