The findings confirmed earlier studies on mice and rats that demonstrate the cardiac benefits of a restricted calorie diet.

The study looked at the heart function of 25 members of the Caloric Restriction Society, ages 41 to 64, who consume 1,400 to 2,000 nutritionally balanced calories per day. They were compared with 25 people who eat a typical Western diet, consuming 2,000 to 3,000 daily calories on average.

The result: Those limiting caloric intake had the heart functions of much younger people -- typically about 15 years younger than their age. Ultrasound exams showed group members had hearts that appeared more elastic than most people their age; their hearts were also able to relax between beats in a way similar to hearts in younger people.

Simply Eating Less Not the Answer

"This is the first study to demonstrate that long-term calorie restriction with optimal nutrition has cardiac-specific effects that [delay or reverse] age-associated declines in heart function," said Luigi Fontana, lead author and assistant professor of medicine at Washington University in St. Louis.

The study will be published Tuesday in the Journal of the American College of Cardiology.

Fontana said simply consuming less food is not the answer. Members of the study group eat food resembling a traditional Mediterranean diet, focusing on vegetables, olive oil, beans, whole grains, fish and fruit. They avoid refined and processed foods, soft drinks, desserts, white bread and other sources of "empty" calories.

For the general public, the researchers recommend a moderate reduction in calories, combined with moderate, regular exercise.

Caloric Restriction, Optimal Nutrition

Research on mice and rats indicated that life span can be stretched by about 30 percent with stringent and consistent caloric restriction. That research also suggested that restricting calories can help prevent cancer.

Heart attacks and strokes cause about 40 percent of deaths in Western countries, researchers said. Cancer causes another 30 percent. Fontana said those deaths are attributable to "secondary aging" from high cholesterol, diabetes, high blood pressure and other often-preventable conditions.

While it has long been known that a healthy diet and exercise can reduce risks, the study suggests that caloric restriction combined with optimal nutrition can do even more.

Fontana said most participants in the study had immediate relatives who suffered heart attacks or strokes, so it was unlikely their genetic makeup was a contributing factor to their unusually healthy hearts.

"We don't know how long each individual will end up living, but they certainly have a longer life expectancy than average because they're most likely not going to die from a heart attack, stroke or diabetes," said professor John O. Holloszy, who worked on the study. "And if, in fact, their hearts are aging more slowly, it's conceivable they'll live for a very long time."