Trading doughnuts for decades?

Diet: Many animal studies show drastic calorie restriction leads to longer life - or maybe it just seems longer.

Medicine & Science

October 13, 2003|By David Kohn | David Kohn,SUN STAFF

Michael Rae is on a diet. A serious diet.

Subsisting largely on "loads and loads and loads of vegetables," he consumes 1,800 to 2,000 calories a day, about 25 percent fewer than the USDA recommends for adult males.

"In truth, I'm a little bit hungry most of the time," he said. "You get used to that, although it can be distracting." The regimen has lowered his libido and can also make him snappish.

One other fact about Rae - unlike most other dieters, he's already thin. Very thin - 6 feet tall and 117 pounds.

So why on earth does he torment himself? The 33-year-old technical writer from Calgary, Alberta, thinks his sacrifice will buy an extra 10 to 20 years of life. That makes him willing to forgo cheeseburgers forever: "I'd much rather be alive and not eating pizza than dead."

Rae might be unusual, but he is not a kook. His regimen is backed by a long list of animal studies showing that "calorie restriction" (CR), as it's called, can significantly prolong life.

Hundreds of studies on yeast, worms, mice and other animals have shown that cutting calories by a third increases life span by about 30 percent. For humans, that would mean an extra quarter-century.

The diet also reduces the risk of many age-related ailments, including heart disease, diabetes and high blood pressure.

Although it hasn't been scientifically tested on people, most researchers on aging think the regimen will work for Homo sapiens. "It would be shocking if it didn't work in humans," said MIT molecular biologist Leonard Guarente. "It works in such a wide variety of critters. Why would it not work in humans?"

Hundreds of hardy believers have already decided that the animal data are persuasive enough. "This is the only anti-aging regimen that has a lot of evidence behind it," said Brian Delaney, president of the CR Society, an international support group.

Delaney (5 feet 11 inches and 137 pounds) is a 10-year veteran of the diet. The 40-year-old philosophy instructor, who lives in Stockholm, now consumes 1,800 calories a day - a 300-calorie increase from the even-more-spartan version he followed until three years ago. That diet crossed the line, he says: "I was ferociously hungry all the time."

Those on the diet admit that CR has side effects, including hunger, chills, low libido and moodiness. It's also a hassle to make special meals and make sure the food has enough vitamins and nutrients.

But the potential payoff is worth the trouble, practitioners say. And there are immediate benefits: Rae and others say they rarely get sick, need less sleep and generally have fewer health problems.

No one knows for sure how CR works. Most researchers think that cells respond to chronic underfeeding by boosting defense mechanisms that protect them from damage and deterioration.

Some scientists liken the process to hibernation, during which cells slow down and take cover when conditions become less hospitable.

"Mild metabolic stress seems to protect cells," said neuroscientist Mark Mattson, who studies calorie restriction at the National Institute on Aging (NIA) laboratory in East Baltimore.

Mattson (5 feet 9 inches and 120 pounds) follows his own calorie-restricted diet. A gaunt, intense 46-year-old, he skips breakfast altogether; lunch is three pieces of pita bread and a piece of fruit; dinner consists of vegetables, more fruit, some nuts and maybe a small serving of fish. His wife and two children don't follow the diet, so at home, he makes his own meals.

"It's no big deal," said Mattson, who lives in Bel Air. "After two weeks, you're not hungry anymore."

In the lab, Mattson has found that the benefits of CR extend to the brain: In mice, the regimen protects brain cells from animal models of neurodegenerative diseases, including Alzheimer's and Parkinson's. He also discovered that intermittent fasting - feeding the mice every other day - improves results even more.

Despite the encouraging results from animals, calorie restriction has not been studied in people. Human CR trials face daunting obstacles. A study of life span would last decades - a complex and expensive undertaking. And there's an issue of compliance: Would participants stick to a regimen that can feel close to starvation?

"There will never be a good clinical trial. People won't stay on the diet," said Guarente.

Primates are the closest relatives studied. Since 1987, NIA has been watching 120 rhesus monkeys at a federal research center in Poolesville. Half get a normal, low-fat diet; the other half get 30 percent less than that. So far, the hungry monkeys score higher on a range of key health measurements.

"It seems very promising," said NIA gerontologist George Roth, one of the study's leaders. But the final results won't arrive for more than a decade. The monkeys, which live for an average of 25 years, are still only in middle age.

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