Celebrity personal trainer Gunnar Peterson's client list reads like a who's who in Hollywood: Kim Kardashian, Jennifer Lopez, and Sofia Vergara, just to name a few.

Now you can get the same access A-listers have via The Gunnar Challenge. The 8-week online fitness program, launching May 21, provides customized exercises and low-calorie meal plans to each user, as well as personal messages from Gunnar himself.

One thing Kim, Jennifer and Sofia are known for are their famous hourglass figures. Toofab's Lawrence Yee asked the celebrity trainer for his tips on getting a small waist and bountiful booty, and his thoughts on all the Hollywood fad diets. Watch the interview, below:

"I think you would have to go with the squat," Gunnar says of his go-to butt exercise, but outlines other alternatives, including lunge variations, leg presses and reverse hyperextensions.

Seems simple enough, but getting the body you want is half physical and half mental. "You're in the driver's seat of your health," Gunnar explains. "You hear about people [saying] 'this is my priority, this is my priority,' and then they won't even make time to work out. Then it's not really a priority!"

If you are looking to get in Hollywood shape and want to learn more about The Gunnar Challenge, head over to the website here.

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