Pilates was my introduction into fitness. The workout challenges your core with the end result being a longer, leaner, and more-toned you. And if you keep with it regularly, you'll be showing off a set of sexy, sculpted abs. Celebrating the feminine form, it's the kind of workout that delivers a body that looks great on camera, something that these 15 starlets know all too well. From Reese to Cameron, see who in Hollywood loves them some Pilates!