Calories Get Blame For Aging Restricting Diets Lengthens Life Of Rats, Researchers Say

Key hallmarks of aging can be prevented or delayed by cutting back on calories in late middle age, new experiments in aging rats suggest.

Previous work in rats, mice, monkeys and other species found that lifespan can be extended 20 percent or more when strict calorie-restricted diets are imposed starting in childhood or young adulthood - an unrealistic and potentially unhealthy approach for humans.

The new results are the first to suggest caloric restriction can have anti-aging effects even when started relatively late in human life - about 45 years old.

The results also strengthen a theory that says aging is the result of biological damage inflicted by oxygen molecules called free radicals. These highly reactive oxygen molecules are a byproduct of metabolism and are produced by the body in quantities proportional to the amount of food consumed.

The anti-aging value of caloric restriction has yet to be tested directly in humans; most people in the world who eat very little also are hobbled by malnutrition. But researchers said they believed the rodent results would hold true in people who eat very low-calorie, nutritionally balanced diets.

The new study, in the July issue of FASEB Journal, published by the Federation of American Societies for Experimental Biology and released Sunday, shows that muscle cells in old rats resemble those of very young rats if the old rats began caloric restrictions as late as 17 months after birth - equivalent to the 40s in people.

Caloric restriction is the only method proven to increase maximum lifespan - the longest that members of a species can live. But there are drawbacks to relying on the method, researchers said. The diet must be formulated to make sure all key nutrients are present. And there is the not insignificant problem of persistent hunger.

Monkeys kept on restricted diets are clearly ravenous much of the time and often go into a frenzy at feeding time.