Diabetes trends in Japan.

The prevalence of diabetes is increasing in Japan, and it is estimated that more than 12 million Japanese people are hyperglycemic. This high prevalence is most likely the result of a complex interplay between genetic and environmental factors specific to Japan. The lifestyle and diet of the Japanese population have changed significantly since the end of World War II. In general, the Japanese have become more sedentary and they consume more fat than in the past. Among Japanese men, these changes have been associated with a steadily increasing body mass index (BMI), a well-known risk factor for the development of insulin resistance, impaired glucose tolerance, and diabetes. Genetic characteristics common to many Japanese may also contribute to their higher prevalence of diabetes. The Japanese have a higher prevalence of polymorphisms for at least three genes that code for proteins thought to play key roles in lipid and glucose metabolism: the beta 3-adrenergic receptor, the peroxisome proliferator-activated receptor gamma, and calpain-10. The interaction between changes in lifestyle and the 'thrifty' genotype characteristic of many Japanese people may play a significant role in the increasing prevalence of diabetes and associated cardiovascular risk in this population.