Scientists have known for years that eating less is healthier but these new findings shed light on how caloric intake affects certain genes responsible for aging.
In the study, researchers compared muscle cells taken from 5-month-old adult mice and 30-month-old "senior" mice.
"The unique thing here is that the overall calorie level, the volume, the amount of food, can also extend life," says Dr. Robert N. Butler, President of the International Longevity Center.
The researchers said their findings could lead to drugs that may slow the aging process - and might also help explain the aches and pains that age brings.
"At the molecular level in muscle, normal aging looks like a state of chronic injury," Tomas Prolla, a professor of genetics at the University of Wisconsin, said in a telephone interview.
Prolla, Richard Weindruch and their colleagues at the university and at the adjacent Veteran's Administration Hospital have been trying to explain study after study that shows restricting food intake, while keeping the diet nutritious, can slow down the aging process.
Evidence has been demonstrated in mice, rats, and humans.
But some heath experts are skeptical and say sacrificing crucial nutrients in an effort to reduce calories is a dangerous idea.
"There are many factors that impact longevity, caloric intake is one, genetics is another, family history has an effect and physical fitness is a factor," says Maureen Storey of the Center for Food and Nutrition Policy.
Of more than 6,000 genes examined from the cells, just under 2 percent showed dramatic changes with aging. Prolla said that, on the genetic level, the cells clearly looked injured.
Some genes slowed down with aging, while others seemed to swing into action, Weindruch said.
So-called heat shock genes, which help repair damaged proteins, became more active as the mice aged. Energy metabolism slowed and genes associated with the repair of damaged nerve cells kicked in.
But putting the mice on a diet stopped the process. Mice who got only 76 percent of the usual calories, but whose feed was enriched so that they did not suffer from malnutrition, had their genetic changes "remarkably" reduced.
"Most alterations were either completely or partially prevented by caloric restriction, the only intervention known to retard aging in mammals," the researchers wrote.
For those who wish to unlock the secret to living longer, dieting isn't an omnipotent factor, says Dr. Butler.
"Diet isn't in a vaccumn," says Dr. Butler. "Diet has to be in the context of activity so that no one can successfully diet without having physical exercise of some sort," he says.
Wendruch said it could be that as an animal ages, it must devote more energy to fixing damaged cells and less to building strong, healthy cells. Dieting basically transformed the metabolism, the researchers said, helping it slow down.