(MODEL RELEASED IMAGE). Tama Matsuda, 100 years old, and her daughter-in-law Keiko, 75, with beni imo -purple Okinawan potatoes that they are eating for lunch. (Supporting image from the project Hungry Planet: What the World Eats) The Matsuda family is one of the thirty families featured in the book Hungry Planet: What the World Eats (p. 186). 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.