Nicole Richie: Sushi, Salad, and Spanx!

Nicole Richie doesn't ever want to be fat again and that's why she eats sushi and salad all day. She also hasn't let having a baby stop her from going out to the bars and clubs. Apparently this isn't the only thing keeping Nicole tiny. OK! can reveal the star's slimming secret isn't some miracle diet or fitness routine, but waist-cinching undergarment Spanx! "She sometimes wears two pairs at a time," a pal of Nicole reveals to OK!. And while the new mom is keeping this secret from the public, her fiance Joel Madden, 28, is all too familiar with them. "He'll help her find them in her closet if they're running late," says the friend. "But he thinks she looks great just the way she is."