07/19/2012 at 05:00 AM EDT
Like many new moms, Jessica Simpson
was eager to get her pre-baby body back after giving birth
to daughter Maxwell Drew
on May 1.
"For me, I really want to do something that is a lifestyle," Simpson, 31, told PEOPLE later that month. "In the past I've been known to yo-yo diet."
So in late May, the designer started Weight Watchers – for which she's a spokesperson – and has been focused on losing weight gradually.
"She understands it's a process," a Simpson friend tells PEOPLE, adding that the star is "working very hard and she's excited."
As for rumors that there's a deadline for her
to lose her post-baby bulge, a rep for the weight-loss company says that's untrue.
"Weight Watchers is in it for the long haul," says a spokesperson. "We're with her 100 percent as she develops a whole new relationship with food and activity."
For more on Jessica Simpson's post-baby slim down, pick up the new issue of PEOPLE on newsstands everywhere Friday