In most of the world, the prospect of living to age 100 sounds like a mixed blessing. While a long life is generally good, many people worry that it also equals diminished health and mental function. But that isn't so in the "blue zones."

In four hot spots around the globe, people live to 100 in great numbers. But it's not only about longevity—they live with strength, vitality and happiness. Residents of the blue zones regularly exercise, tend their gardens, are active members of their communities, eat delicious food and even have sex!

To find out what they're doing right—and we're doing wrong—Oprah and Dr. Oz look to Dan Buettner, a freelance writer for National Geographic who spent seven years researching his book The Blue Zones: Lessons for Living Longer from the People Who've Lived the Longest.