The Nobel Prize in Medicine, awarded to three scientists for their study in cell biology, specificly telemeres. Telemeres are at the end of chromosomes. When the cell replicates, the telemers shorten. This is one of the reasons why we grow old. Caloric restriction has shown that telemers last longer, therefore a longer life span.
That's how I understand it. It's interesting that science is understanding this at the cellular level.