Caloric Restriction Linked To Longevity

Scientists at Harvard Medical School, in collaboration with scientists from Cornell Medical School and the National Institutes of Health, have discovered the connection between caloric restriction and longevity.
A significant decrease in calories can extend longevity by as much as one third.

The link is affected through two genes and mitochondria:

"When cells undergo caloric restriction, signals sent in through the membrane activate a gene called NAMPT. As levels of NAMPT ramp up, a small molecule called NAD begins to amass in the mitochondria. This, in turn, causes the activity of enzymes created by the SIRT3 and SIRT4 genes--enzymes that live in the mitochondria--to increase as well. As a result, the mitochondria grow stronger, energy-output increases, and the cell's aging process slows down significantly. (Interestingly, this same process is also activated by exercise.)"