The secret of longevity could be just as simple as eating less. Comprehensive and wide-ranging research by scientists from Salk institutes, published in the journal Cell, found that caloric restriction (CR) could delay the cellular functional decline related to aging. In other words, eating less could slow down the degenerative processes in our cells that occur with aging. 
While the effect of CR has been explored before, this was the first attempt to see its effect on cellular pathways. The team, situated in the US and China, used animal experiments to study the effect of CR. They studied 56 rats, controlling their diets from 18 months to 27 months. In human years, this would be the equivalent of controlling diet through 50 to 70 years of age.
In all, they studied 168,703 cells from 40 cell types. These included different organs of the body, including, bones, kidneys, aorta, muscles, liver, fat, and brain. They measured the activity level and the overall composition of the cell, comparing the older participants with the younger participants.
Rats on CR did not show many of the changes associated with aging that were found in rats on a normal diet. More importantly, their cells and tissues resembled those of younger rats. The team found that 57 percent of the changes associated with aging were not found in rats on CR. One of the most marked effects was on immune cells in almost every tissue. This level of change was negligible when compared to rats on a normal diet.