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.