Middle-aged adults who began eating five or more fruits and vegetables every day, exercising for at least 2 1/2 hours a week, keeping weight down and not smoking decreased their risk of heart disease by 35 percent and risk of death by 40 percent in the four years after they started.

"The adopters of a healthy lifestyle basically caught up. Within four years, their mortality rate and rate of heart attacks matched the people who had been doing these behaviors all along," said Dr. Dana King at the Medical University of South Carolina, who led the research.

That is not to say people should wait until their 40s or 50s to get on track, he added.

"But even if you have not had a healthy lifestyle previously, it's not too late to adopt those healthy lifestyle habits and gain almost immediate benefits."

King and his team set out to find if late-starters could reap the rewards of habits like eating vegetables and walking 30 minutes a day.

Living longer
When they had picked up all four habits, they enjoyed a sharp decline in heart disease risk and in death from any cause.

It took all four - having just three of the healthy habits yielded no heart benefits and a more modest decrease in overall risk of death.

Still, said Dr. Nichola Davis at the Albert Einstein College of Medicine, "these benefits are on a continuum. The more of the healthy habits that you can adapt, the better. ...These are modest changes that they're talking about."

King's team took age, gender, race, and other risk categories for cardiovascular disease into account, although King said the converts likely took up other healthy life changes - such as cutting down on salt or upping their calcium intake - that might have contributed to their health benefits.