Fresh goya (bitter gourd) and other vegetables are considered one of the reasons for Okinawan's longevity. Naha City Makishi public market. Hara hachi bu: "eat only until 80 percent full," say older Okinawans. The island has been the focus in recent years of researchers trying to discover why a disproportionately large number of Okinawans are living to age 100 or more. (Supporting image from the book Hungry Planet: What the World Eats.)