But the diet may cause problems of its own, such as weakened bones. Researchers are now looking at the diet's possible benefits — and risks — for people. Human-trial findings can't come soon enough for Snir, who learned about the diet while surfing life-extension Web sites. "We'd have to wait a lifetime to get a definitive answer," he says. "So at some point I just decided to take a leap of faith."
Some longevity researchers say he's making a pretty safe bet; skeptics wisecrack that he'll certainly feel like he's living longer.
"As if we haven't heard that one before," says Brian Delaney, 40, who runs the Calorie Restriction Society, an online support group for about 1,000 followers of the diet. An American living in Stockholm, Sweden, Delaney has experimented with degrees of CR for a decade, hitting as low as 1,400 calories a day. Now he eats 1,800 calories, which leaves the 5-foot-11-inch man a wispy 135 pounds.
He grumbles that calorie restriction has gotten a bad rap; followers have been lumped with cloners, corpse-freezers and other life-extension "cults." Who's crazy, he asks: baby boomers who spend billions on antioxidants, human-growth hormone injections and $50 wrinkle creams, all with no scientific basis? Or calorie counters who've chosen the "only anti-aging approach backed by mainstream science?"
Diet like hibernation
Scientists don't know exactly how CR lengthens lives, but they know it goes beyond the mere health benefits of being thin. They compare it to hibernation; physical processes that cause wear and tear on the body are drastically slowed.
One leading theory says it works by curbing cellular pollution. When cellular "factories" convert food to energy, they release byproducts known as free radicals. These biochemical ruffians wreak havoc on cells, genes and tissues and have been blamed for age-related changes ranging from crow's-feet to increased cancer risk. When a body metabolizes fewer calories, it's like a car that uses less fuel — there's less free-radical pollution.
CR also may reduce levels of sugar in the blood, suppress hormones that promote cell growth and rouse genes that promote longevity. Any or all of these factors could play a part in slowing the aging process.
Researcher Mark Mattson's pet theory is the "healthy stress" hypothesis. A neuroscientist at the National Institute on Aging (NIA) in Baltimore, Mattson showed CR protects mouse brain cells from developing Alzheimer's and Parkinson's diseases. He also found that feeding mice every other day extended their lives as much as slashing total calories, even though the mice gorged themselves on feeding days. He took this to mean that hunger, whether temporary or chronic, subjects the body to a healthy form of stress that makes cells hardier. Think of the cardiovascular benefits of wind sprints. Now Mattson is about to test what happens when people eat all their food in a four-hour period and fast the rest of the day.
Mattson, a slight 120 pounds at 5 feet 9 inches tall, skips breakfast and has been counting calories since he began studying CR 20 years ago. He does it not to live longer but because he's convinced it reduces the risk of dreaded diseases.
Research under way
Whether calorie restriction extends human life poses a formidable research question. To prove it would require closely following the dietary intake of hundreds or thousands of people for decades. And that assumes subjects would agree to stick to a deprivation diet.
Despite the challenges, the NIA is taking the first step with three pilot studies across the country. The one-year studies will first test whether a 30 percent restricted diet is doable and safe for a few hundred volunteers. Sneaking ice cream won't work; researchers are using a metabolic test to determine exactly how many calories people eat.
Dr. Evan Hadley, an NIA associate director spearheading the research, says they also will examine markers such as blood-sugar levels, blood pressure and free radicals. "The studies won't tell us if calorie restriction makes people live longer but it should give us a clue if the immediate effects in humans parallel what we see in mice," he says.
The best evidence may come instead from our branchmates on the evolutionary tree. In a laboratory in Poolesville, Md., about 75 monkeys are on a 30 percent restricted diet; another 75 eat as much as they like. The NIA study is in its 16th year and captive monkeys usually live about 25 years, so it's too early to tell if CR will lengthen their lives. But tests already hint at positive trends, including healthier hearts and less cancer among the hungry monkeys.
In the absence of human — or even final monkey — results, scientists are split on whether CR is a reasonable step for humans. Mattson says as long as people commit to the daunting task of getting all their vitamins and minerals despite eating less, he thinks it's a healthy diet.
Dr. Itamar Abrass, head of geriatrics at Harborview Medical Center, isn't so sure. "I think there's a benefit in humans; I'd be surprised if there wasn't," he says. But the devil could be in the details, he says.
Without human studies, no one knows when to start or stop the regimen. Starting before sexual maturation could stunt reproductive development, but waiting too long could reduce the payoff.
And while CR may make for a slender, healthy 30-year-old, it may make for an excessively frail elderly person.
People who are already doing CR are "truly experimenting on themselves," Abrass says. "That's OK, but I certainly wouldn't recommend it."
Diet downsides
Even for a diehard like Snir, the diet has downsides; severe hunger pangs and a lowered libido top the list. His hands are sometimes so cold he has to wear gloves while working on the computer. And he's often low on energy. The biggest sacrifice, he says, was giving up mountain biking because it demanded too much energy. Oh, and then there's cheesecake, which he speaks of wistfully.
But Snir, at 5 feet 10 inches tall and 170 pounds, has managed to avoid the gaunt appearance and weakened bones typical of his CR brethren by eating a lot of protein powder and lifting heavy weights. And he is undeterred. Even if he's hit by a bus tomorrow, forgoing French fries will have been worth it, he says. After battling his weight for most of his adult life, the diet helped him drop 30 pounds. Plus, striving for a longer life, he says, made him realize he'd better make it a life worth living — so he began spending more time with his wife and kids.
His wife, Adi, feeds herself and their four young children a diet full of grains and vegetables, but she doesn't count their calories. She takes Micky's aspiration to live longer as a compliment: "It must mean he likes the life he has with me."
She knows how his regimen must look to outsiders. He weighs nuts and doles them out of pill bottles to make sure he's eating the right amount of protein, and he dines at precisely 10 a.m., 2 p.m., 6 p.m. and 10 p.m. He once barged into the kitchen of an exasperated dinner-party host and grabbed morsels off the stove when a meal wasn't served promptly.
The fact that Snir has stuck with any diet this long, much less one so stringent, sets him apart from most. Knowing how difficult the diet is, many scientists are studying calorie restriction hoping to uncover an age-defying mechanism they can exploit the profitable way — with a pill. No aging cure appears likely within a decade, but already scientists have identified a molecule in red wine that mimics the effects of CR in yeast. They've also spied a gene that seems to change when faced with too-few calories.
But Snir, an ascetic at heart, pooh-poohs the search for a magic pill. "It's like those commercials with the belts that are supposed to shock your belly and give you abs," he says. "Quick fixes never work. People need to be willing to make an effort to make their own lives better." |
