After years of staying slim on a humble diet of fish, vegetables and rice, Japanese are developing a sweet tooth. That's proving a business opportunity for Krispy Kreme and other chains from the U.S., a nation famous for knowing a thing or two about fattening food.

Since opening in December, Japan's first Krispy Kreme Doughnuts Inc. store is drawing long lines for an hourlong wait or longer just to get in. In the first three days, 10,000 people came to the shop.

"The texture was fluffy and sticky, unlike any other doughnut," said Yoji Yahagi, 22, who stood in line with his girlfriend to eat two chocolate doughnuts each.