From PEOPLE Magazine Click to enlarge
It's the phone call every leading lady dreads: After signing up to play the title role of Winnie Mandela in a biopic back in November, Jennifer Hudson was asked not once, but three times by director Darrell James Roodt to lose weight before filming began. That left the actress-who gave birth to her son David Jr. last August (Dad is WWE wrestler David Otunga, 30)-a solid six months to shed her post-pregnancy pounds. The request "didn't faze me that much," she says, but she tried to temper expectations nevertheless. "She was saying, 'I'm going to do my best, but I can't promise anything,'" recalls Roodt. "Meanwhile, she really went for it. That was amazing."

The same could be said for the results. A size 16 when she made her big-screen debut in 2006's Dreamgirls, Hudson told PEOPLE she is "so happy" to show off her newly toned size 6 body at the Cannes International Film Festival this month. "I'm in the best shape of my life!" says Hudson, 28. But the former American Idol contestant-who famously gained more than 20 lbs. for her Oscar-winning turn as Effie White-didn't resort to extreme measures. "Whatever it takes to morph into the character, I'll do it," she says. But "I wasn't going to starve myself for anyone." Instead Hudson joined forces with L.A.-based trainer Harley Pasternak in the fall. In January she also signed up to become the celebrity spokeswoman for Weight Watchers. Since then, "she keeps getting tighter and thinner," says Pasternak. "It started off being about Winnie, and it ended up being a whole new JHud."

Her transformation started with a new approach to food. "I've done a lot of diets in the past," says Hudson, who often would eat only grilled chicken and egg whites until she got bored and fell off the weight-loss wagon. "I was restricting myself." Now she's learned how to eat in moderation and enjoy smaller portions of her favorite foods like pizza and sushi. "She was very afraid of carbs," says her Weight Watchers counselor Liz Josefsberg, who taught Hudson how to measure her servings with a food scale. "Jennifer fully understands that there are no off-limits indulgences as long as they are portion-controlled," says Josefsberg. Now, "I don't get hungry," says Hudson. "I just eat right." She also consistently breaks a sweat. Just four days after giving birth to David Jr., the new mom started walking for 30 minutes each day before amping up her workout to Pasternak's five-day, 25-min. circuit training regimen. "I'm a cardio maniac!" says Hudson.

Still, there are days Hudson doubts that she can really fit into her new size 6 wardrobe. "In my head, I am still the same weight I was before," she says. "It takes a while to get used to it." Luckily, she has plenty of time to adapt to her new reflection in the mirror. "This is the way I want to be," says Hudson, "and the way I want to stay!"

  • Contributors:
  • with Monique Jeseen/Cannes,
  • Dana Kennedy/Cannes,
  • Thailan Pham/New York City,
  • Michelle Tan/New York City.