LOST
40 lbs!
in eight months

Tucked into a well-worn couch in the living room of her Los Angeles home, Valerie Bertinelli flashes her famous girl-next-door grin as she talks about what she is looking forward to during the holidays. There's the tree to put up in its usual spot by the fireplace and, says the actress with a laugh, "I am jonesing to cook Christmas dinner!" But there is one annual tradition Bertinelli, 47, finally plans to give up: For the first time in more than 30 years, her list of New Year's resolutions will not include any mention of dieting. "Every year since I was 13," she says, her eyes tearing up at the admission, "I have sworn to lose weight."

So what makes 2008 any different? Well, for starters, there's the 40 lbs. Bertinelli has oh-so-publicly dropped since March as a Jenny Craig spokeswoman. But slimming down isn't anything new for the actress, who admits to yo-yo dieting most of her life, starting even before she landed her breakthrough role at 15 as cherub-cheeked Barbara Cooper on the hit '70s sitcom One Day at a Time. "I'd get to a certain place," she says, "and be like, 'Oh, okay, I'm fine here—and then [I'd relax] and back, back, back would come the weight, plus some."

What has changed for her, she says, is the way she now thinks about eating. "It's about taking the time before food goes in your mouth to be aware," she says. "Am I aware that I'm eating this? And am I eating it because I'm hungry—or because I need to soothe myself?"

Bertinelli's identity as an emotional eater ("I'm Italian—I don't have to be sad to eat, or happy to eat; it could be anything," she says) made her decision to up her weight loss goal from 30 lbs.—which she hit the first week of August—to 40 lbs. particularly bold. In recent years, she says, she has struggled to come to terms with her 2001 split from Eddie Van Halen and how it affected their son Wolfie. "I feel guilty for not holding my end of the bargain and keeping this family together," she admits. Then, alluding to Van Halen's well-documented battles with substance abuse, she adds, "If I could have done anything else but separate from Ed to make sure Wolfie had a full family, I would have done it. But sometimes it's better to divorce so your kids can have a better life."

This summer brought with it another challenge: Wolfie, now 16 and a bass player, asked her if he could go on tour with his dad's group. "I still have mixed feelings" about the decision to let her young son hit the road with a rock band, says Bertinelli; not only did she worry about him, she also found it lonely being without him. "I'm so thrilled because when he came home for five days and yelled, 'Hey, Ma,'" Bertinelli recalls, "I started to tear up, and I went, 'Wolfie, you have no idea. I've been dying to hear that for the last 2 1/2 months!'"

But even though Bertinelli didn't turn to food for comfort, she says losing those last 10 lbs. was still tough. "You're not as vigilant as you are in the beginning," she says. So how did she do it? By shaking up her five-times-a-week exercise routine, mixing in sprinting, jumping and squats with her regular long walks and elliptical machine workouts.

Of course, she did have the extra incentive of a return to the spotlight when it came to shedding those last few pounds: In October she became a regular correspondent on daytime television's The Rachael Ray Show, and this spring she'll embark on a tour to promote a book she's finishing up. ("Not the typical memoir" is all she'll say.) Through it all, she has had her friends and family alongside her—including boyfriend Tom Vitale, 46, a private equity investor whom Bertinelli began dating in 2004, three years after she and Van Halen called it quits on their two-decades-long marriage. "It's been a pleasure to see Valerie trying on new outfits," he says. "We went shopping for swimsuits, and she was in the dressing room calling out to me, 'Tom, could you bring me a smaller size?'"

Although Bertinelli remains happily unmarried ("I don't want to plan a wedding!" she says), two years ago she and Vitale exchanged rings: an antique diamond for her, and for him, a platinum band with five diamonds symbolizing Wolfie and Vitale's four children (ranging in age from 8 to 16) from a previous marriage. "We are very much together," she says.

Even though Van Halen didn't make it to the blended-family Thanksgiving celebration in Scottsdale, Ariz., this year (he's always welcome, says his ex), Bertinelli had something extra to celebrate: She had recently hit her goal weight. And although she won't reveal what that number is, she does say, "It's the one on my drivers's license—I haven't been there in 10 years!"

So did she celebrate without turkey and stuffing? Hardly. "I've learned how to have a bite of dessert," says Bertinelli. "It shouldn't be about denying yourself." Not that Bertinelli could, given her love of cooking. On one Rachael Ray segment she taught the talk show host how to make gumbo. "It was unbelievable!" Ray says. "She is tremendous in the kitchen."

With her weight finally under control, Bertinelli is free to set her sights on new goals, which include taking the last two credits she needs to get her high school degree, running a half-marathon—and climbing a mountain. "I'm so excited to have lost this weight," she says. "For the first time, I feel I have turned a corner. I've changed my life."

Go behind the scenes at Bertinelli's PEOPLE photo shoot! Visit PEOPLE.COM/VALERIE_VIDEO