Jessica Simpson Is

Jessica Simpson Is 'Working Very Hard' to Lose Weight: Friend

Jessica Simpson

Justin Campbell/BuzzFoto

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