Ashlee Simpson: Bronx Keeps Me Fit!

Forget personal trainers – celeb mom Ashlee Simpson has a better way to keep on fitting into those skinny leather jeans: she says son Bronx, 20-months, gives her quite the workout.

“I have lots of stairs at my house and my son is 33lb now, so I carry him up the stairs a lot," she said in a recent interview.

But it looks like Bronx can't take all the credit for Ashlee's toned abs. “I definitely hit the gym. I’ll do 30 minutes when he’s down for a nap. I’ll do 30 minutes of cardio and I also like a class called Cardio Barre [aerobic-ballet workout].”