200 Pounds Beauty (2006)

Based on a Japanese manga, Kanna-San, Daiseikou Desu, this story revolves around Kang Han-na, an overweight phone sex employee and secret vocalist for Ammy, a famous Korean pop singer who actually lip syncs as she cannot sing. After getting humilitated publicly by an ungrateful Ammy, Han-na undergoes an extreme makeover to become a pop sensation herself.