Low Insulin Not Calorie Restriction Lengthens Your Life
February 08, 2003
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
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.
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.
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.
January 24, 2003;299:572-574