The connection between eating less and living longer has been known to researchers since the 1930s when a Cornell University nutrition professor unexpectedly discovered that dieting rats tend to live 30 percent longer. Same results have been foundwith fruit flies, monkeys and Labrador Retrievers. If that's the case with animals, then it might be truewith humans too. This is the premise behind the calorie restriction diet (CR).
"Aging is a horror and it's got to stop right now," said Michael Rae, a vitamin researcher from Calgary, Alberta, and a board member of the Calorie Restriction Society, which has about 900 ultralean members worldwide. "People are popping antioxidants, getting face lifts and injecting Botox, but none of that's working," he said. "At this moment, C.R. is the only tool we have to stay younger longer." It's worth mentioning that Mr. Rae is 6 feet tall, weighs just 115 pounds and is often very hungry.
Advocates of C.R., insist they're not dieting to get skinny but rather to have the last laugh. Eat smart enough, they say, and you can live to see great-great-grandchildren, not to mention postpone the onset of cancer, diabetes, heart disease and kidney failure.
Historical data supports this idea. During the first and second World Wars, the shortage of food in some northern European countries led to a sharp decrease in mortality from coronary artery disease, Type 2 diabetes and cancer, according to Dr. Luigi Fontana, a geriatrics researcher at Washington University in St. Louis.
Those rates surged again after the wars, he said. Likewise, on the Japanese island of Okinawa, where residents have traditionally followed a diet similar to that of C.R., an unusually high number of people have lived a century or more.
Even the US government had entered the picture. Investing $20 million to see if the regimen really works for people.
Just how exactly does CR works, nobody has the the complete picture yet. Scientists know for sure 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. Some suspect eating less slows the rate of cell division in tissues. Others theorize that hunger triggers a survival mode, activating genes that help resist stress and protect vital organs. Meanwhile, biogerontologists are racing to invent drugs that mimic the effects of calorie restriction without all the carrots and cottage cheese.
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.
To prove that eating less calories do indeed lengthen human lifespan, Dr. Mattson will begin in January the first major study on the long-term effects of meal skipping on humans. Men and women between the ages of 40 and 50 will be screened to see how blood pressure, cholesterol, immune function and other markers respond to one daily meal versus three.
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Another institute study already underway at three university research centers (Washington University, Tufts and Louisiana State) is looking at whether lighter meals reduce the risks of age-related chronic diseases - like heart disease and Alzheimer's - and lead to longer and more productive lives.
The one-year studies will first test whether a 30 percent restricted diet is do-able 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 comes not from mice but from our primate cousins. 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.
There's no shortage of skepticism about calorie restriction in the scientific community. An article in this month's issue of The American Journal of Preventive Medicine, the leading journal on obesity research, concluded that caloric intake was not as important in staving off death by cardiovascular disease as other factors, like physical activity.
"A focus on calories alone doesn't strike me as the way to live a long life," said Dr. Michael Alderman, a professor of medicine at Albert Einstein College of Medicine, who contributed to the article, which examined the results of a 21-year study of nearly 10,000 subjects. The healthiest people in the survey exercised regularly, which requires eating more, Dr. Alderman said. "If you're burning fuel, you've got to feed the engine with more food."
|"When subjects lose 15 to 20 percent of their body weight, they sometimes start binge eating after restricting calories for a period. Others can become clinically depressed."|
|- Dr. Itamar Abrass|
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. Thomas Wadden, director of the Weight and Eating Disorders Program at the University of Pennsylvania School of Medicine, warned that extreme dieting like an ultralow-calorie regimen can lead to mental health problems.
"There's no question that people who fixate on food this much can develop mild obsessive-compulsive disorder," he said. "This behavior can also precipitate an eating disorder. When subjects lose 15 to 20 percent of their body weight, they sometimes start binge eating after restricting calories for a period. Others can become clinically depressed."
"Some people might like this diet, but most people won't last half a day on it," he said. 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.
Last summer, Dr. David A. Sinclair, an assistant professor at Harvard Medical School, discovered that a chemical commonly found in red wine could vastly increase life span. Okay, so the chemical, resveratrol, only worked with yeast and fruit flies in his experiments, but Dr. Sinclair, 34, is an optimist. "It could be a revolution in medicine," he said, if it were made into a pill. "If we're able to switch on the body's own defenses the way calorie restriction seems to, we could be talking about an end to cancer, stroke, heart attack and all the other age-associated diseases."