Kathy Kaehler starting working with Julia Roberts when Roberts landed her role in America's Sweethearts. Kaehler designed a workout that would give Roberts more energy, and also sculpt her long and lean frame through strength training and yoga- and Pilates-inspired moves. You can try the exercises yourself by reading Kathy Kaehler's Celebrity Workouts.

"Exercising with Kathy has changed my life in a great, subtle and consistent way," Roberts says. "I must admit, I don't love exercise, but I do love how I feel afterward: accomplishment, clarity, energy, strength, joy. These are all things I give myself through working out, and I can feel it in everything I do."

Now that Roberts is based in New Mexico with her family, she has taken a hiatus from training. "And I am sure she is very happy to be there, away from all the hoopla," Kaehler says. "She was so, so, so impressive. She had it so under control. When I saw her after she had had the twins, I was just really happy for her. But it is daunting. It is overwhelming. You don't know how you're going to respond – mentally, physically, hormonally."

Kaehler says Roberts is bouncing back from her twins' pregnancy remarkably well. "She didn't gain that much weight," Kaehler says. "She has already e-mailed me that she is taking Pilates in New Mexico. I don't see that she will have any problem."