Can Calorie Restriction Lengthen Longevity?

Every morning I turn on the television just in time to hear Willard Scott from NBC's "Today Show" attempt to pronounce the names of America's centenarians. Whenever I see the ages next to the faces on that rotating jar of Smuckers, I can't help but wonder, what are these super-senior citizens doing right?

As humans, it's our business in life to stay alive for as long as possible. Each year, millions of dollars are poured into studies aimed at discovering the fountain of youth. The latest fountain du jour? Calorie-restrictive diets.

Several reports, including an ongoing study at the Wisconsin National Primate Research Center (WNPC), have shown that calorie restriction can extend the life expectancy of primates, mice and fruit flies. Canto, a 25-year-old rhesus monkey at WNPC, looks and acts like a monkey half his age thanks to being fed a diet that contains 30 percent fewer calories per day than the average rhesus monkey for the past 17 years.

Compared to his balding, arthritic-ridden one-year younger counterpart, Owen, who has been fed a typical rhesus monkey diet, Canto's shiny coat, elastic skin and what researchers describe as a "youthful energetic demeanor" clearly demonstrate the positive effects of a calorie restrictive diet...on rhesus monkeys.

Now, here's the problem.

"There's been no scientifically peer-reviewed research on humans," says Keri Gans, MS, RD, CDN and American Dietetic Association spokesperson. "That's the gold standard on research. It's premature in taking one study that was successful in rats and saying that it would work in humans."

A January 2009 segment on 60 Minutes featured members of the Calorie Restriction Society (CRS). Followers consume only 1,100 to 1,800 calories per day, compared to the 2,000 to 2,500 recommended allowances for adult females and males, respectively.

During the segment, members were pictured "enjoying" a CRS-friendly cocktail hour complete with low-calorie soup (their version of a Bloody Mary) and a walnut and green bean puree mixture (yes, it was baby food) dabbed onto flour-free bread. Yum.

Their mantra: "If I'm hungry, I know number one that I have done what I meant to do. I've eaten less than my body thought it wanted," 15-year CRS veteran Meredith Averill, 62, told 60 Minutes.

"Hunger is a health signal that [your body] needs to be refueled," says Gans. "These people are taking it too much to an extreme."

While CRS members have lowered their blood pressure, reduced body fat and lessened their risk factors for heart disease, diabetes and even cancer, there's been no solid evidence that a calorie-restrictive diet does indeed lengthen your lifespan.

In fact, researchers from the University of Southern California's School of Pharmacy and the University of North Texas Health Science Center found that calorie restriction does not benefit already fit mice or humans. In one case, caloric restriction begun in fitter, older mice actually shortened their life span.

"My concern is that [people] are putting themselves at a high risk for a nutrition deficiency," says Gans. "We need fuel to run properly. Without it, people are going to get tired, fatigued, dizzy and dehydrated. Their productivity, concentration and ability to exercise can decrease."

If you're obese or overweight and consuming more than your recommended calorie limit, reducing your calorie intake to lose weight and get healthy is one thing. But according to today's research, if you're already fit and active, slashing daily calorie intake may work against you.

Here's the bottom line: If you're already at a healthy weight, consume a healthful, balanced diet and maintain an active lifestyle, calorie restriction isn't for you. After all, maintaining a diet of walnuts and baby food isn't only dangerous--it's boring. And unless you're a rhesus monkey named Canto, it doesn't even guarantee that you and Willard Scott have a date with a jar of Smuckers.