(CNN) -- As movie stars and supermodels put their best foot forward on the silver screen or the red carpet, they make sure to flaunt their hips, abs and arms, too.
Hillary Swank, one of Valerie Waters' clients, trained for "Million Dollar Baby" for three months -- four hours a day, six days a week.
Hailed by magazines and television shows as the standards of beauty and fitness, celebrities seem to have bodies the average American could never attain.
According to the National Institutes of Health, the average American woman has between 22 and 25 percent body fat, and the average man between 17 and 19 percent, putting both men and women above their recommended percentages and out of synch with the svelte celebrity standard.
CNN recently spoke with five celebrity trainers, who, without hesitation, say their star clients have to work just as hard as anyone else to achieve their weight loss and fitness goals. The main difference between training a celebrity and training any other client, they say, is scheduling.
"The only difference is possibly the hour that I'm training them," said Valerie Waters, who trains celebrities like Kate Beckinsale and Cindy Crawford.
Waters said that when her celebrity clients aren't working on a project, she's able to train them during regular business hours. However, when they're filming a movie, schedules can get crazy. "I've often trained Jennifer Garner at four o'clock in the morning," Waters said.
Michael George, who helps tone Reese Witherspoon and Tobey Maguire, said the only difference between training celebrity clients and other clients is often a tighter deadline.
"If I have to get them ready for a project and I've only got six weeks, or two months, that's a lot more pressure on them than it would be to just get ready for the summer to wear a bikini, or for overall health and maintenance," he said.
"It's different for someone with a nude scene coming up on September 22, the script's already done and the story board is laid out," said celebrity trainer Gunnar Peterson, who has worked with Jennifer Lopez, Angelina Jolie and Matthew McConaughey.
"You've got to work backward from specific goal dates," Peterson said. His challenge is to come up with effective, time-restricted workout programs and then translate them into something more permanent after filming deadlines come and go.
Fine-tuning the 'Perfect 10'
So, what kinds of fitness goals do celebrities have when they already seem to have the perfect package?
"Please tell everybody it's not true!" Waters said. "They have to work for it too. And it only seems like that because you're seeing them after they've been on an exercise program for a month."
"My clients stay that way because they're consistently exercising three times a week, and they're eating well 80 percent of the time," she said.
"A lot of celebrities are in good shape or look pretty good when they call me to work with them, because they are their own product," George said. "As such they have to look good, and the better they look, typically, they will make more money. That's the way Hollywood sort-of works."
Ashley Borden, who's worked with Mandy Moore and Christina Aguilera, said looks can be deceiving.
When celebrities are seen on the red carpet, "Everything is styled, fit, planned to emphasize the positive," Borden said.
"They're a human being just like everybody else," she said. "Except for the fact that most of them make more of an income than you or I do on a day-to-day basis, so they have more access to help. But certain people are celebrities because they're genetic celebrities. That's why you're a supermodel, because you're a genetic celebrity. They didn't hire you because you're the smartest person in the room, you just happen to get the best look."
Although debates about sickly skinny models center around their unhealthy habits, Waters said people with naturally slim bodies need to maintain their gazelle-like shapes through exercise and a healthy diet.
"Even supermodels have to work out. You may have nice long legs or whatever, but if you want to have muscle tone, you need to lift weights," Waters said. "It doesn't stay toned unless you're fourteen."
Waters has trained with Cindy Crawford for 15 years, and said, "You don't get much more genetically perfect than that."
"And yet Cindy works out with me three times a week," she said, "through work, through babies, pregnancy, post-pregnancy. And she does it. I think she's quoted as saying, in her 20s she had the body God gave her, in her 30s she had the body that she worked for."
Not all celebrities consistently look perfect. Like many people, they become pregnant, develop health problems or take poor care of themselves, and end up out of shape.
"A lot of times I get calls from production companies, directors or producers, or the clients themselves, and they call me because they're in really desperate need of changing their body and lifestyle," George said.
Celebrity trainers have various philosophies when it comes to training, but most tailor their regimens to fit seamlessly into their clients' hectic lives.
Celebrity trainers create a plan their clients can stick to, with exercises that can be done out of the gym while traveling or on location, and diet plans that accommodate night after night of fundraisers and awards show dinners. Here's how some of them do it:
Training philosophy: "Get in, get out, get a life." Waters' workouts last less than an hour, incorporating circuit training with weights and a "kitchen purge" to clear out bad food which she replaces with healthy options.
Best tip: "Don't be afraid of weights. They're the quickest way to change your body"
Training philosophy: Peterson creates different workouts for different clients every day. He has clients eat protein early in the day, making breakfast the largest meal and dinner the smallest.
Best tip: "Get on a regular routine. Exercise should be a cornerstone of your life, like brushing your teeth. It's not even an option to blow it off."
Training philosophy: As one of Karl List's master trainers, Borden focuses on mio-fascial release, or deep tissue stretching; biomechanics with resistance and balance exercises; cardio, proper water intake and diet. She suggests drinking 100 ounces or water a day and gives her clients cardio homework, which they track using a heart rate monitor.
Best tip: Take care of the arches in your feet. "When your arches collapse, your knees rotate inward, and your hips rotate outward giving you a saddlebag appearance. It then pulls your sternum down, it pulls your neck forward, and everything collapses." She suggests orthotics and mio-fascial release to combat chronic pain and posture problems.
Training philosophy: George varies his workouts to keep clients engaged. He borrows from Eastern and Western philosophies, using martial arts, yoga, Pilates and meditation in conjunction with strength training. He saves time by using multiple muscle groups in each exercise, like a squat with a bicep curl. He also incorporates pliometrics and core boards.
Best tip: Don't wait too long to integrate a healthy diet and consistent exercise into your days. "I've seen a lot of people come to me when it's a little bit too late," he said, "I've had [clients] pass away due to illnesses, cancer, heart disease, whatever it may be. The time is now. If you don't put your health first you're never really going to truly be happy."
Training philosophy: Greene tries to look at the entire individual and get clients to visualize how doing all the exercises he suggests will improve their lives. He says the physical benefits are almost meaningless if they don't translate to "you having a better life overall ... especially those areas not related to fitness."
Best tip: "First thing is, know what you want," Greene said. He said a lot of people want to work out because it's "in" or they know they should be doing it, but don't have a specific goal. "Know the reason you are making these changes in your habits, what is it you really want to achieve." He also said most people need to do both weight training and cardio. E-mail to a friend