Kim Kardashian and Miley Cyrus' respective trainers talk about how they keep their celebrity clients in shape.

NEW YORK CITY, NEW YORK, UNITED STATES (JANUARY 03, 2013) (REUTERS) -  Every January magazine stands are packed with workout and diet secrets of the stars.

While some seem unobtainable, long time celebrity trainer Gunnar Peterson, who trains everyone from Kim Kardashian and Sofia Verga to Sylvester Stallone and Jennifer Lopez, said achieving the perfect body starts with one's self.

"When you see the people, or when I see the people at the tops of their field, whether it's a sport or entertainment, or lawyers, God forbid. The ones who are at the tops of their field always seem to have that same work ethic. And I think that maybe that's the message," said Peterson who has been training Hollywood A-listers for 20 years.

Some have accused reality star Kim Kardashian of having a fake rear-end, however, Peterson said the expectant mother trains hard.

"Kim's not a stranger to working out and she will do whatever it takes to get the job done and as you can see it's definitely see, it's definitely working," he said.

One of the main excuses people give for not working out is 'not having time,' which Peterson said is one of the largest obstacles for his Tinsel town clients.

"Sofia is someone who fits this into an incredible busy schedule. All the people at the top of their game, the biggest challenge is to find a way to fit their exercise program into their schedules," Peterson told Reuters.

But if time is still a factor pilates might be the way to go.

"One of the reasons that a lot of people are drawn to pilates is because they know that it's fast, they know that if they do pilates correctly that they're going to get the results that they want in a two-three week time period," said pilates expert Mari Winsor.

Winsor has worked with Marisa Tomi, Emma Stone, Samuel Jackson and recently received attention for helping Miley Cyrus transform her body.

"She really took to pilates, I mean she's young, she's healthy. She had some left over remnants of body from when she was a little kid and she wanted to feel like a women, she wanted to change her body, she wanted to have her arms sculpted. Most of all she wanted her tummy sculpted and her legs and her thighs to change," Winsor told Reuters.

Model Miranda Kerr combines pilates with other workouts in order to stay in tip-top shape: "I'm pretty consistent with my yoga, pilates and also resistance training. So I'll workout, all of that, like at least three to four times a week."

While fellow cat walker Brooklyn Decker opts for a more rigorous routine: "Everything, anything physical, hiking."

Soul singer Chaka Khan recently dropped pounds to manage her diabetes. Along with a strict liquid diet, the singer turned her bed into one of her workout environments.

"My favorite exercise is resistance exercise. Where I have my bands, I can lay in the bed in do them," she told Reuters.