A lot of it is based on a healthy diet and copious exercise. However, there is another factor that seems to have a huge impact on Okinawan's longevity that can'r be measured quantifiably: self-sufficiency and positive outlook. There are stories of a 105-year-old woman hunting down a poisonous snake and killing it with a fly swatter. Or an instance of a 96-year-old man defeating a thirty-something in a marshal arts competition.
Self-sufficiency and a purpose in life seems a powerful indicator in how long someone is going to live. Multiply this outlook by the entire community and it is easy to see why Okinawa has such a thriving elderly population.