I think there is a different in genetic information between the ancestor Japanese(Asian people) and Western people base on the environment basic, cause Western whether tend to be colder than Asia whether, i think so the people there need to store up more fat to keep body warm and in hot whether in Asia they do not necessery to stores up fat to keep their body warm. Because these genes existed in the ancestor so even though an Asian may move to a cold whether enviroment, but still remain slim as they inherited the genes from the Asian ancestor. I don't know :-), i just have a lecture on genes at Uni so i thought this is the reason
