Caloric restriction leads to longer and healthier life

By David Liu, Ben Wasserman and edited by Sheilah Downey

University of Wisconsin researchers published a paper in the journal Science suggesting that eating fewer calories leads to a longer and healthier life.

Early studies in flies, worms and other low animals like rodents show that eating fewer calories greatly extends lifespan. But some researchers play down the findings suggesting that the benefits of caloric restriction may not apply to humans.

The new study shows a nutritious but reduced-calorie diet blunts aging and significantly delays the onset of diseases like cancer, diabetes, cardiovascular disease and brain atrophy in monkeys.

Dr. Richard Weindruch, of the UW-Madison School of Medicine and Public Health, lead author of the study, said "We observed that caloric restriction reduced the risk of developing an age-related disease by a factor of three and increased survival."

During the 20-year study, 50 percent of monkeys that ate freely survived while 80 percent of the monkeys given the same diet, but with calories reduced by 30 percent, were still alive.

Weindruch said "There is a major effect of caloric restriction in increasing survival if you look at deaths due to the diseases of aging."

In the study, the animals that ate calorie-restricted diet had 50 percent lower incidence of cancers and cardiovascular disease than those eating freely. And the researchers observed that diabetes in animals eating calorie-restricted diet was non-existent while it was commonly seen in the animals that ate food without any restriction.

Additionally, calorie-restricted diet also benefited brain health.

Sterling Johnson, a neuroscientist in the UW-Madison School of Medicine and Public Health said "It seems to preserve the volume of the brain in some regions. It's not a global effect, but the findings are helping us understand if this dietary treatment is having any effect on the loss of neurons" in aging.

Specifically, the parts of the brain that are responsible for motor control and executive function like working memory and problem solving were better preserved in animals that ate fewer calories.

One previous study

One previous study led by researchers at Saint Louis University and published in the June 2008 issue of Rejuvenation Research has already found some evidence to support the hypothesis that calorie restriction may be able to extend a person's lifespan.

The researchers tested the theory is that calorie restriction slows aging by decreasing the level of a thyroid hormone called triiodothyronine (T3) in the body, which in turn slows metabolism and tissue aging.

For the study, Edward Weiss, Ph.D., associate professor of nutrition and dietetics asked one group of volunteers to follow a diet with its total energy cut by 300 to 500 calories, and one group to follow a regular diet, but did exercise regularly and a control group did not cut calories nor did much of physical exercise.

The volunteers were sedentary, non-smoking men and post-menopausal women aged 50 to 60 with average or slightly above average body mass indexes. They were free of cardiovascular disease, diabetes, lung disease, uncontrolled hypertension and evidence of malignancy when entering the study.

During the one-year follow-up, volunteers in both the calorie restriction and exercise groups experienced similar change in body fat mass. But the volunteers in the calories restriction group, not other two groups experienced lower levels of the thyroid hormone.

A long term study is needed to determine whether reducing T3 levels through calorie restriction slows the aging process, according to the researchers. But the current study resulted in some evidence to suggest a possibility that T3 may be involved.

It is logically possible when intake of calories is low, human bodies would slow down their metabolism and other biochemical processes, and conserve the energy for more adverse condition the body may have to deal with in the future. As a result, calorie restriction leads to slower aging process.