Women's gyms are mushrooming in Tokyo, attracting those who want to work out and lose weight without having to worry about men viewing their exertions.

"Gyms for women will explosively increase if they can win their hearts and the news spreads by word of mouth," an industry source said.

U.S. fitness chain Curves operates some 9,000 gyms in 31 countries and is opening three gyms in Tokyo this summer.