“Just bought all the girls in my @weightwatchers group pedometers to track their steps,” Simpson Tweeted Thursday. “10,000 steps a day = 5 miles! Let’s step it up!”
Simpson’s philanthropic turn comes almost two months after joining Weight Watchers in late May.
“There’s not a goal weight – I just want to feel normal and fixate on inches,” she told PEOPLE at the time. “I really want to set small goals, so I’m constantly reaching goals and not looking at something so far ahead.”
Meanwhile, a friend says the starlet is committed to her exercise routine. “She understands it’s a process,” a Simpson friend told PEOPLE, adding that the star is “working very hard and she’s excited.”
For more on Jessica Simpson’s post-baby slim down, pick up the new issue of PEOPLE on newsstands everywhere Friday