Best anti-aging trick? Start eating less

updated 1:47 p.m. ET July 8, 2008

While the quest for the proverbial Fountain of Youth is endless and typically fruitless, one method known to extend the human lifespan by up to five years has quietly become accepted among leading researchers.

The formula is simple: Eat less. It could add years to your life, several experts now say. And done in moderation, it could at least help you live a more healthy life.

The only question is: Will the average person do it?

While little short of a nip-and-tuck will make you look younger, calorie restriction, as it is called, is as close to a real Fountain of Youth as any known technique comes. Even scientists who are cautious about anti-aging hype say it works, both by cutting risks for some diseases and by allowing all body cells, somehow, to hang in there longer.

"There is plenty of evidence that calorie restriction can reduce your risks for many common diseases including cancer, diabetes and heart disease," says Saint Louis University researcher Edward Weiss, who last week announced a new study that brings fresh understanding to how it works. "And you may live to be substantially older."

By the numbers
Here's a rough rule of thumb that many experts generally agree on now: Eat 15 percent less starting at age 25 and you might add 4.5 years to your life, says Eric Ravussin, who studies human health and performance at the Pennington Biomedical Research Center in Louisiana.

One important caveat: Ravussin's estimate is based mostly on studies of other animals and only preliminary research in humans. But the work by Weiss and others is unlocking the mysteries of aging and suggesting the animal studies apply to humans.

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"There is absolutely no reason to think it won't work," Ravussin told LiveScience.

Perhaps even more promising, though in early stages of research, are drugs designed on the basis of what's been learned from calorie-restriction studies. Those drugs would target human cells to deliver the same benefits, turning off bad things and turning on good things to extend cell life in general, or offer new therapies and cures to vexing diseases like Alzheimer's and cancer.

If you can hang in there until these promising new drug therapies are developed, you may live in a world where lifespan increases by 10 to 15 years, researchers say.

Don’t plan on living to be 200, Ravussin said, "but I think we're going to gain quite a few years."

Mysteries remain
Scientists aren't sure exactly why calorie restriction slows aging. But they're on the verge of a firm understanding. In a nutshell, it is thought to lower metabolic rate and cause the body to generate fewer damaging "free radicals."

One hypothesis is that it decreases a thyroid hormone, triiodothyronine (T3), which then slows metabolism and tissue aging.

Weiss and colleagues studied men and women, aged 50 to 60, who did not smoke, were not obese and were in good health. The volunteers were split into three groups — a calorie-restriction group, an exercise group, or a control group — and followed for one year. The calorie-restriction group cut back by 300 to 500 calories per day. (A typical healthy adult diet should include about 2,000 calories.) Volunteers in the exercise group maintained their regular diet and exercised regularly.

While both the calorie-restriction and exercise groups experienced similar changes of body fat mass, only those in the calorie restriction group also experienced lower levels of the thyroid hormone. A longer-term study is still needed to pin down whether reducing T3 levels through calorie restriction indeed slows the aging process as suspected, the scientists say.

The results were published in the June issue of the journal Rejuvenation Research.

Step-by-step
Weiss' work advances the body of anti-aging knowledge, said Christy Carter, an aging researcher and assistant professor at the University of Florida College of Medicine.

"The more that scientists can demonstrate similar biological profiles between rodents and humans with regards to calorie restriction, the greater the possibility that lifespan extension will translate to human as well," Carter said.

Weiss figured it's sensible to take steps now. You can cut 300 to 500 calories by simply skipping dessert or substituting a turkey sandwich for fast food. A nutritional diet and exercise are important to any weight-loss effort, Weiss and others caution.

"Our research provides evidence that calorie restriction does work in humans like it has been shown to work in animals," Weiss said. "The next step is to determine if this in fact slows age-related tissue deterioration. The only way to be certain, though, is to do a long-term study."

Others agree: more research is needed.

"I think that they've documented a real and interesting effect of caloric restriction in humans," said UCLA evolutionary biologist Jay Phelan. "But they are still a long way from demonstrating that it changes human lifespan at all."

Proven in animals
Evidence that calorie restriction boosts lifespans in rodents is solid. Christiaan Leeuwenburgh of the University of Florida's Institute on Aging showed in 2006 that eating just 8 percent less and exercising a little more over a lifespan can reduce or even reverse aging-related cell and organ damage in rats.

Various studies have shown that cutting calories by 20 to 40 percent significantly both extends life and, with a little exercise, leaves old animals in better shape.

Eating fewer calories  also reduces age-related chronic diseases such as cancers, heart disease, and stroke in rodents. That's important because it suggests ways to not just make us live longer, but to allow us to age more gracefully, healthwise.

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