Scientists say fewer calories equals longer life

Even though scientists already knew at least as far as animals are concerned, that reducing the calorie intake was linked to longevity, they never really knew why.

A new study suggests that restricting calories in order to lose weight may also make people live longer.

The scientists from Harvard Medical School believe that they have discovered the secret to extending life expectancy.

They say that the food restriction of mainly calories produces a molecular response which starts a chain reaction in the "power house of the cells" known as the mitochondria.

The mitochondria keep cells healthy and alive, and when the mitochondria weaken and do not function well cells begin to weaken and grow more susceptible to DNA stress, and eventually die.

Using human cells in a lab, scientists found that cutting down on calories but not nutrients, strengthens the mitochondria by increasing the activity of enzymes created by two genes called SIRT3 and SIRT4, thus slowing down the aging process of that cell.

Molecular biologist David Sinclair says as yet they are not sure which particular mechanism is activated by these increased levels of NAD, which then affect SIRT3 and SIRT4.

Sinclair says the two genes, SIRT3 and SIRT4, produce proteins that go into the mitochondria, the little energy packs inside cells that are very important for staying healthy and youthful.

He says as we age, we lose them and they become less efficient.

They are also very important for keeping the cells healthy and alive when they undergo stress and DNA damage during the aging process.

Sinclair says by restricting calories the normal cell-suicide programs are noticeably attenuated, and they believe these two genes may be potential drug targets for the diseases associated with aging.