She won't divulge exactly how she lost the weight. But on her web site she says, “I sought the advice of doctors, reviewed different options and designed a long-term health plan …. I eat healthier, drink lots of water and exercise regularly.”

“She did it on her own—no trainer,” a pal says of the Less Than Perfect star, who lost about 30 lbs. One trick? Working out to foreign-language tapes, Rue told Extra.

To go from a “momish, roundish” role in Prime to a slender fashion editor in The Devil Wears Prada, she swam and, she says, “I have been pushing the wine bottle away—at least after the first glass. I have to fit into these clothes.”

All it took to put on nearly 30 lbs. for In Her Shoes was pizzas and milk shakes. Dropping them? “It is tough losing the weight,” she told reporters.

After losing more than 10 lbs. in prison, Stewart has kept her shape with morning yoga and hikes in the woods near her Bedford, N.Y., home, says friend (and Being Martha author) Lloyd Allen. She also weight trains and does up to 250 crunches at a time. “Being healthy is at the top of her list,” says Allen.

The star of The Practice and author of Wake Up, I'm Fat! says she started exercising and eating healthier in 2003, “mostly to be really present for my son [Milo, now age 4]. It was a good decision for me as well.”