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All but the last bite

Leave a little on your plate after every meal if you want to live to 100, suggests author Dan Buettner, who studies so-called Blue Zones: areas around the world where people tend to live longer and healthier. In Japanese culture, he says, people stop eating when they feel only 80% full—a practice that has helped the country earn a top spot on the world's-oldest-people list.

Next: Two meals a day