06/07/2012 at 12:00 PM EDT
Five weeks after giving birth to her baby girl Maxwell
, Jessica Simpson
appears to be fitting in a little time for herself.
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!