4 Celebrity Workout Moves for Summer

— -- How do red-hot, red-carpet stars like Rihanna, Katy Perry and Megan Fox stay so fit and fabulous?

For answers, “Good Morning America” turned to Michele Promaulayko, Yahoo Health’s editor in chief, and celebrity trainer Harley Pasternak as part of the “GMA” Yahoo Your Day series.

Promaulayko weighed in with easy ways you can help your body burn more fat, including a tip about what, if anything, to eat around your workout.

“Choose snacks that work for you, so a combination of protein and fiber,” she said. “Protein actually boosts your metabolism and the fiber keeps you fuller longer.

“You don’t really need to fuel your workout, nor do you need to eat right after because, if you do that, you’re just going to offset the calories you worked so hard to burn,” Promaulayko added.

Celebrity trainer Pasternak demonstrated his quick, A-list workout moves to help you fit it in.

If you want to get model Behati Prinsloo’s sculpted arms, Pasternak recommends doing a modified press-up.

“Lay on the ground … put your hands shoulder-width apart with your palm down,” he said. “From this position, you’re going to press up as high as you can and then you’re going to come down two-thirds of the way and press up.”

To get Megan Fox’s killer abs, Pasternak suggests a plank.

“You’re going to imagine there’s a string that goes from your tailbone and you’re being pulled straight up towards the ceiling,” he said. “Keep going and keep all the weight on your toes. Make sure your heels don’t move back.”To achieve Lady Gaga’s to-die-for derriere, Pasternak suggests doing a single leg hip thrust.

Pasternak says to lie on your back and push your hips as high as you can. “Just when you think you can push them no higher, push them higher,” he said.

Finally, for Jessica Simpson’s flawlessly toned legs, Pasternak recommends a Bulgarian lunge.

“The weight is going to be on your left leg, specifically your arch and heel,” he said. “We’re going to go down and up … switch sides.”