updated 06/07/2012 AT 12:00 PM ET
•originally published 06/07/2012 AT 12:30 PM ET
Simpson, 31, was seen wearing sweats, oversized sunglasses and a big smile while out and about in a car in L.A. Wednesday. According to the photographer, the new mom went to a private gym.
The star has signed on to work with Weight Watchers to lose the baby weight.
“I think anybody who’s gone through a pregnancy, after they have the baby, it’s like, ‘I need to do something about this,’ ” she told PEOPLE. “For me, I really want to do something that is a lifestyle, because in the past, I’ve been known to yo-yo diet.”
Looks like may be getting an early start!