By Kwiyeon Ha TOKYO (Reuters) – Competition is cutthroat among Japan’s thousands of pop idol wannabes, but a unique concept is winning fame for a band of “chubby” girls deploying their cheeky cuteness to combat prejudices against obesity. Despite one of the lowest rates of obesity in the developed world, Japan has a growing number of underweight young women, who rely on excessive dieting to satisfy society’s emphasis on being slim. Enter “Pottya”, a pop group named after a slang word for chubby and consisting of four young women who are not especially hefty to Western eyes, but well above average weight in Japan.