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Item #8
Low
Insulin, Not Calorie Restriction Lengthens Your Life
Less
insulin equates to less fat which affects longevity.
A
lean body devoid of fat may be more significant in determining
lifespan than a calorie-restricted diet, according to a new study of
genetically altered mice.
The
mice in the study were able to eat whatever they wanted and still stay
slim because their fat tissue had been altered so it could not respond
to the hormone insulin. Insulin helps to move sugar from the blood
into the body’s cells and also helps fat cells to store fat.
Researchers
altered the insulin receptor gene in the fat cells of lab mice, and
since insulin is needed to help cells store fat the mice had less fat
and were protected against obesity.
The
altered mice ate 55 percent more food per gram of body weight than
normal mice, yet had 70 percent less body fat by the time they reached
3 months of age.
Moreover,
the altered mice lived 18 percent longer than normal mice, and after
three years all of the normal mice had died, but one-quarter of the
altered mice were still alive.
Previous
studies have shown that a calorie-restricted diet can extend the
lifespan of everything from yeast to mammals. One theory for why this
occurs is that eating less produces fewer chemical by-products, known
as free radicals, which can damage cells. However, the current study
suggests that leanness may also play a role in promoting longevity.
The
findings could open the possibility of a new drug that would fight
obesity, and related illnesses like type 2 diabetes, by blocking
insulin receptors in fat tissue. The drug would need to be targeted to
fat only, however, as a loss of insulin sensitivity through out the
body results in type 2 diabetes, researchers noted. Science January 24, 2003;299:572-574
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FACT:
Individuals are gaining, on average, 14-16 pounds in
eight years.
Using
the NHANES and CARDIA data, Hill and his colleagues estimated that -
an average of 1.8 – 2.0 pounds each year.
Assuming that each pound of body weight gained represents 3500
calories, the researchers calculated that 90 per cent of the
population is gaining up to 50 extra calories a day. The body does not
store excess energy with 100 per cent efficiency, however. Hill’s
team estimated that for every 100 extra calories consumed, at least 50
would be stored as fat. The article appears in the 7 February issue of
the Science.
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