Less Body Fat = Longer Life

Jan. 23, 2003 -- Carrying around less body fat -- rather than eating fewer calories -- may be the secret to living longer.

A new study looks at this issue of longevity, which researchers admit is dependent on numerous factors: genetics, hormonal and growth factors, body weight, body fat, and environmental factors.

Actually, "the effects of restricted calories on life-span has been studied in mice for more than 60 years," writes Matthias Bluher, a researcher with the Joslin Diabetes Center at Harvard Medical School. Some studies have suggested that reduced food intake is more important than having less body fat, he writes. However, it has been difficult to determine exactly which factor is most important.

His study appears in the Jan. 24 issue of Science.

Of the 250 mice in Bluher's study, half were specially bred to lack a response to the hormone insulin specifically in their fat cells -- he calls them "FIRKO mice." These mice were unable to store body fat. The normal mice were able to gain weight and body fat as usual.

Bluher fed all the mice a normal mouse-style diet rather than a restricted-calorie diet. They lived in an environment that simulated normal light-dark days.

The normal mice lived normal mouse-length lives -- 30 months. But at 30 months, 80% of the FIRKO mice were still alive. In fact, they lived an average of 5 months longer than the control mice. At 36 months, all the control mice were dead. However, about 25% of the FIRKO mice were still alive -- with one living to 41 months.

"The FIRKO mouse demonstrates the beneficial effects of reduced [body fat] in a setting where food intake is normal or even increased," writes Bluher.

His study suggests that increased metabolism is the secret to the FIRKO mouse's leanness and longevity, Bluher says.

SOURCE: Science, Jan. 24, 2003.