Average Uk Women Does Anyone Know The Real Reason Why Japanese Women Are Usually Thinner Than The Average Western Woman?

Does anyone know the real reason why Japanese women are usually thinner than the average western woman? - average uk women

I hear it only because of genes that the Japanese are generally small and tend not gained too much weight. But this can not but the only reason for the significant difference between the average weight of women in the United Kingdom and in Japan women? ... Or not? siiigh, Japanese girls are so happy:)