Dr. Rosedale has a fantastic response: the longevity of the Okinawans and Kitavans:
First of all, population studies are the least scientifically robust form of health science. That being said, there are many speculations of why Okinawans have a high number of centenarians. Firstly, we must distinguish between increasing maximal lifespan that CR has been shown to do and I believe my diet can also do, and increasing average lifespan. Increasing average lifespan is nice but not near as powerful as extending youth and increasing maximum lifespan. For that there are no human counterpart and we have no footsteps to follow, only science as revealed in animal studies. That being said, the Okinawans eat considerably more fish than other groups and a higher percentage of carbohydrates as vegetables i.e. fiber as opposed to starches. Most of the fiber gets excreted, so Okinawans are likely relatively calorie restricted. Also, overindulging in food among Okinawans is very frowned upon. What Nick Lane has said in his book “Oxygen” is the following, p 275; “based on a 25 year study, the book [The Okinawa Way written by a Japanese cardiologist] argues that the secret of the Okinawans... goes beyond genes, diet, and exercise to their relaxed lifestyle and low level of stress. The Okinawans have a word for it, "tege", which means 'half-done': forget timetables, forget finishing today things that can be done tomorrow. I suspect they are probably right.”
In the most comprehensive study pertaining to the Okinawan diet and longevity entitled, "Caloric Restriction, the Traditional Okinawan Diet, and Healthy Aging" published in the Annals of the New York Academy of Sciences, the following was found; “Findings include low caloric intake and negative energy balance at younger ages, little weight gain with age, life-long low BMI...and survival patterns consistent with extended mean and maximum life span." The study concluded; "This study [Caloric Restriction, the Traditional Okinawan Diet, and Healthy Aging] lends epidemiologic support for phenotypic benefits of CR in humans and is consistent with the well-known literature on animals with regard to CR phenotypes and healthy aging."... I have not seen a breakdown of the calories eaten, but it's known that they eat more fish and fibrous vegetables and lower calories. Simple logic could conclude that they eat fewer non-fiber carbohydrates, which, along with reduced stress, may account for their increased average lifespan.
Though my knowledge of the Kitavans is less, I believe much the same applies to them, and there are similar myths based on poor science and falsities that is being written about them that unfortunately is getting much unwarranted publicity.