Credit: Michael Rozman/Warner Bros.

Three weeks into the Dancing With the Stars competition, Ricki Lake is a lean, mean dancing machine!

"I lost more than 13 inches in a month. It's crazy," she told Ellen DeGeneres in a talk show appearance airing Thursday.

Whittling five inches from her waist and five inches in her hips, Lake, 43, credits her DWTS pro partner Derek Hough with encouraging her to move more.

"The Derek Hough diet is the best," Lake quipped. "It's hardcore." Indeed, the former Hairspray star acknowledges her new figure didn't come without a price. In fact, she says it's much harder than it looks to dance week after week.

"[DWTS pros and execs] say it's the hardest thing you will ever do and you're like, 'Yeah, yeah, yeah. I've done hard: I had my baby in my bathtub at home' and yet we work out all day long. We are sweating all over each other!"

And Lake tells Us Weekly that as her body continues to change, so will her DWTS wardrobe.

"I am really getting in great shape," Lake told Us backstage at a recent taping, adding that she's lost about 15 lbs. so far. "I will be wearing less and less clothing the smaller I get. I am feeling more comfortable in my own skin."