Nov. 1, 2006  -- There is growing evidence that severe calorie restriction can dramatically extend your life expectancy.

The Wisconsin National Primate Center has been studying the effects of a low-calorie diet on the aging process in monkeys, and the center is seeing remarkable results.

Canto is a 25-year-old Rhesus monkey just one year younger than his counterpart, Owen.

They are both part of the study. Canto, whom researchers have put on a low-calorie diet for 17 years, acts and looks years younger.

Although Canto would be considered a senior citizen at his age, his coat is still shiny and soft; his skin is elastic; and he has a youthful energetic demeanor.

But Owen who eats twice as much is frail and moves slowly. He is losing his hair, has developed arthritis, and his face is clearly showing signs of aging.

"We've observed that the animals on calorie restriction live longer and that they develop diseases later if at all," said Dr. Richard Weindruch of the University of Wisconsin.

The diet is called a caloric-restriction diet, and involves eating about 30 percent fewer calories per day than the average monkey.

Extensive animal research shows it can help to ensure a longer and healthier life.

Meredith and Paul McGlothlin from New York City have been on the diet since 1994.

Most men eat a typical diet of 3,000 calories a day; Paul eats just 1,900. His diet is filled with protein and all the essential nutrients and minerals.

"I have more energy than I ever dreamed," he said.

There is no definitive evidence of the long-term benefits for humans, but researchers say a restricted diet is helping Canto stay young.

"I think this probably will work. We don't know for sure in people," ABC News medical contributor Dr. David Katz said.

"The effects are almost certainly real, but I think they're out of reach for most of the population. … [Monkeys] don't have holiday parties to go to, and they don't have a workplace where there are all sorts of tempting things," he said.

Although people who adhere to a calorie-restricted diet have a balanced diet, Katz said that he wouldn't recommend it for everyone.