Dr. Dean Ornish is the first doctor to prove that heart disease can be reversed through diet and exercise. His low-fat, high-fiber eating plan has helped millions of people, but he says another key to good health is avoiding stress.

"When you manage stress better, when you exercise, when you eat better, your quality of life improves," he says. He suggests meditation as a way to reduce stress, adding that patients who meditate show improved medical tests.