And yet, from American Journal of Clinical Nutrition, "Rice intake and type 2 diabetes in Japanese men and women: the Japan Public Health Center–based Prospective Study"
Although the prevalence of obesity [body mass index (BMI; in kg/m2 ) .30] in the Japanese is lower than in Westerners (Japan: 3% in both men and women; United States: 31% in men and 33% in women) (3), the prevalence of type 2 diabetes in Japanese populations is not dramatically lower than that in Western populations (Japan: 7.3%; United Kingdom: 4.9%; United States: 12.3%)
This metastudy is a few years old, and it's difficult to compare populations because the definition of "having diabetes" varies by time and location. It's a very compelling subject though. I doubt we'll find a complete answer in the next 20 years, but I know that whatever else, it's going to be part genetic, part behavioral, and I think less dependent on food intake and exercise than we want to believe.