The leading lady's head-turning curves, the Grammy Award winner's killer legs, the television host's enviable abs - we've seen the best that every ultra fit A-lister has to offer. More importantly, we asked all of them how they did it Julianne Hough, Dancer/Musician/Actress This multitalented 23-year-old hates the gym and turns to celeb fitness trainer Tracy Anderson for total-body "dance-y" workouts. When on the road, she mixes up sessions with her trainer and P90X DVDs. After all that hard work, Julianne follows a strict diet. When dining out, her order generally looks like this: a mixed green salad with lemon (and without cheese) and salmon with mixed vegetables - no oil or salt. (Do you have a health-conscious friend like Julianne on your holiday shopping list? Check out these 7 Great Gift Ideas for Health Nuts - plus, more gifts for everyone else in your life!) Marisa Miller, Supermodel/Actress This 33-year-old model is known for her phenomenally flat belly. Her secret? She targets her obliques "Working your obliques pulls everything together and gives you a slim waist," says Marisa. One of her favorite moves is the alternating crunch. Target all of the waist-cinching muscles in your abdomen with these 8 Belly-Flattening Core Exercises. When it comes to keeping a diet on track, she offers this advice: "Eating smart is all about having an awareness of your body. The most obvious way to do that is by seeing it. So when you're trying to lose weight, spend more time wearing less. Selena Gomez, Actress/Musician You would never guess that this multitalented 19-year-old struggled with a junk-food problem. But that is reportedly what landed Selena in the hospital last year. Fast-forward one year and she says she's eating healthier and feeling better! Simple changes like adding more lean protein and vegetables can make all the difference. Gwen Stefani, Musician and Fashion Designer Gwen's weightlifting, boxing, and cardio workouts continue to pay off. The 42-year-old musician and mom is always active. Whether she's skiing, power walking, or chasing her kids, Gwen is rarely sitting down. Whenever possible, Gwen chooses organic, grass-fed, and local food to keep herself - and her family - healthy. Kate Hudson, Actress When Kate's not running after her two sons, Ryder and Bingham, she catches a Pilates session or dance class. She's also a fan of Core Fusion, a mix of yoga, Pilates, ballet, and strength training. As for diet, Kate's trainer Ashley Conrad recommends eating five times a day - making sure to include lots of lean protein. Kristen Bell, Actress At 31 years old, this hilarious actress attributes her killer figure to always taking the stairs. Yoga and strength training twice a week give her sexy muscle definition. As for food, Kristen finds counting calories useful and even comforting because it helps her know she's staying on track. Leighton Meester, Actress Justin Falahi, Leighton's personal trainer, takes her workouts outdoors. Strength-training moves on park benches and playground workouts make for a fun outdoor sweatfest. Before each workout, Leighton takes five minutes to meditate and de-stress, a perfect me-time moment. (Not only does sweating outside feel great, it can help you get in shape faster. Here, 7 Reasons Why You Should Take Your Workout Outside.) Olivia Munn, Actress/Model Running is the one exercise Olivia will not do anymore. At 31, she prefers surfing, hiking, and Pilates. Her healthy-eating guideline is simple: If she can't see it, she won't eat it, so she keeps unhealthy foods at bay. Courteney Cox, Actress At 47, Courteney has never looked better. Interval training, which fires up her metabolism and burns more fat. Courteney's trainer, Michelle Lovitt, varies her cardio between the elliptical and treadmill. Michelle also keeps Courteney's body guessing with resistance-band and power-plate strength training. See the full list of The 25 Fittest Female Celebrities