On average, the Japanese get over 50% of their calories just from rice and over 80% from carbohydrates. They also have the longest lifespans in the world and far lower obesity and heart disease rates than similarly developed places.
To get the long lifespan, low obesity, and low heart disease of an Okinawan you'd have to truly live like an Okinawan... eating exactly the kinds of foods they eat and having little stress, similar sleep habits, and similar genetic dispositions. People have not been successful in replicating the approach elsewhere.
The approach I described is the way to eat to stoke your metabolism and keep your blood sugar low. It's good for fat loss, muscle building, high energy levels, and general good health. There's more to it than I described (such as eating 5 or more times a day), but those are the basics.