Healthy living gives huge boost to lifespan: How many years?

(CBS) Can healthy living really help you live longer? An eye-opening new study from Holland says it can - and the effect can be very dramatic.

Researchers at Maastricht University tracked 120,000 men and women between the ages of 55 and 69. Each person was given a score in 1986 based upon his/her adherence to four key factors that have been shown to affect mortality: smoking, physical activity, body weight, and dietary habits.

What happened? Men who avoided smoking, exercised at least 30 minutes a day, avoided obesity, and stuck to the heart-healthy Mediterranean Diet lived about 8.5 years longer, on average, than men who didn't do any of those things, according to a written statement released by the university.

Healthy living had an even bigger effect on women's lifespans. On average, those who met all four criteria lived 15 years longer than women who met none.

Fifteen years? Eight-and-a-half years? Those are huge numbers, especially given that life expectancy in the U.S. - where healthy living isn't exactly the norm - now stands at 77.9 years.

"I was surprised that the effect was so big," study author Piet van den Brandt, professor of epidemiology at the university, told CBS News. "I was also surprised at the big difference between men and women."

Van den Brandt said he wasn't sure why healthy living women would live so much longer than their male counterparts. One possibility, he said, was that hormonal differences explained the difference.

The study comes at a time when longevity researchers seem to be focusing more on the role of heredity, he said. "I wouldn't cancel out these four factors," he said. "They seem to be quite important for longevity and healthy aging."

The Mediterranean Diet is an eating pattern that emphasizes fruits, vegetables, whole-grain cereals, and low-fat dairy products, fish, tree nuts, legumes, lots of olives and olive oil, and moderate consumption of alcohol, during meals.

The study was published in the American Journal of Clinical Nutrition.