Fitting into sample sizes. Being photographed on the beach in your bikini. Wearing skinny jeans (and actually looking skinny). These are some of the everyday feats celebrities pull off, but not without help from the world's best nutritionists and trainers. Since summer is just about here, and you're likely feeling the same anxiety we are (Bare arms? Not ready! Short shorts? Think again.) we've pulled together a list of celebs' favorite slim-down methods. See what's worked for Gwyneth Paltrow, Gisele, J.Lo, and more.

SoulCycle
Celebrities from Brooke Shields to Chelsea Clinton, Kyra Sedgwick to Tory Burch have saddled up to a bike in this soulful spinning studio. To make pedaling away at stationary bikes more appealing, SoulCycle added complimentary gel seats (your seat will thank them), dim lighting, flickering candles, and killer music courtesy of its top-notch staff. You'll even get an arm workout thanks to a quick toning session with one-pound weights (they're surprisingly heavy after half an hour of spinning). If you can't make it to one of Soul Cycle's 45-minute classes (which can burn 500 calories!), head to their website to download the instructors' favorite tunes, and use them to pump up your own bike workouts.

David Kirsch
Anne Hathaway, Ellen Barkin, Kerry Washington, and Heidi Klum all rely on David Kirsch to get them red carpet-ready. Kirsch works with simple equipment like stability balls and medicine balls to take effective moves to a new level of burn. Since Heidi Klum was famously back on the Victoria's Secret runway in what seemed like a day after giving birth, we were especially curious about her ab routine. Kirsch says oblique crunches are one of the signature moves in her circuit. "Lay on your right side with knees bent, right arm on the floor in front of you, left hand behind your head. Crunch, lifting your knees straight up and bringing your left shoulder toward them; pause, lower and repeat." Kirsch recommends doing 15 reps on each side, 4 times a week. "Focus your energy on engaging your lower abs and not your hip flexors. You should feel it from your belly button downward," he explains.

You can find more of Kirsh's moves in his books and DVDs, and his full range of supplements are available on his website (the metabolism-boosting Thermo Bubbles are a celeb favorite).

Tracy Anderson
Being Madonna's long-time trainer is saying something. But the Material Girl isn't Tracy Anderson's only claim to fame. She also tones Gwyneth Paltrow, and was Gisele's post-baby workout of choice. Need we say more? Anderson is an energetic, petite former dancer who uses dance-based cardio for calorie burning and unique pilates-style moves for body sculpting -- all with her signature twist. Check out the workout she designed for Gwyneth Paltrow to help the star shed pounds in time for "Iron Man 2." You can see the video (and the diet plan) here.

If you don't live near L.A. or NYC where Anderson's studios are, you can follow her workouts at home courtesy of the DVD series.

Dr. Junger
Dr. Alejandro Junger's Clean Program has over 7,000 people signed up for the diet online -- and that was before Gwyneth Paltrow's public praise of the plan (trainer Tracey Anderson included the protein powders in Gwyneth's "Iron Man 2" diet). Dr. Junger -- trained in traditional internal medicine as well as integrative medicine -- believes in an "Elimination Diet" where common allergens and unnatural substances are cut out from your meals (think eggplant, certain nuts, and dairy). "Dairy is not a natural thing to consume for an adult mammal," explains Dr. Junger. "You dont see any other mammal on the planet drinking milk when you stop breastfeeding." Dr. Junger has seen big effects on patients' overall health (and weight) simply by removing this food group."You take people off dairy, and tons of symptoms just resolve," he says.

To shed pounds in time for summer, Dr. Junger recommends that you "replace solid meals with smoothies, juices, and shakes." When you're hungry, "Drink water with lemon." And finally, "Sweat. Either by exercise or infrared sauna." Infrared sauna? We ask what exactly that can do. "Infrared saunas work by promoting or causing sweat, which also mobilizes fat and toxins," Dr. Junger explains. Sounds good to us!

Gunnar Peterson
Gunnar Peterson has made a name for himself training Hollywood's biggest stars (he currently counts Halle Berry, Kim Kardashian, and Jennifer Lopez as clients). To help those starlets shed pounds quickly, he has them do "a ton of cardio" and relies on two principles: keep moving, and pump that blood "from north to south." Clients like Kim Kardashian tone their upper bodies with sets of pushups, broken up with cardio intervals. "Whether it's marching in place or jumping rope, do it for 30-60 seconds and then repeat the first exercise," says Peterson. He then has clients tackle their core with crunches, bicycles, or supermans. "By forcing the blood to go to the upper extremities and then the lower extremities, you're increasing your demands on your heart and getting great cardio," Peterson explains.

As for that lower body, clients like J. Lo do demanding combo moves like the squat/curl/press. "Squat down holding weights by your side, stand up and curl the weights up and then press the weights overhead," says Peterson. If you're concerned about squats bulking up your legs, heed Peterson's advice: "[Squats] will not make you big. Food makes you big," he explains. "Kill the chef, don't kill the trainer."

Physique 57
Kelly Ripa has been vocal about her love of Physique 57 -- she's even convinced the crew and guests of "Live" to try the workouts on air, including Regis and Anderson Cooper. The majority of the class takes place at a ballet barre, where clients perform simple toning exercises (the positions are a hybrid of ballet and pilates) that look easy, but will have your thighs quivering after the first fifteen seconds. One of Ripa's favorite moves is the "Pretzel," where you sit on the floor with one leg bent at 90 degrees in front of you, and the other bend around back behind you. Leaning forward gently on your fingers for support, lift your back knee and foot off the floor and pulse upward to shape the stubborn outer seat area.

Those who can't make it to NYC for the 57-minute classes can now try the workouts via DVD.

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