ABC News' Rachel Smith reports:

Hoopnotica is the latest Hollywood weight-loss craze causing quite the hoopla among celebs.

A favorite with style-watcher Kelly Osbourne, Hoopnotica uses a device like a hula hoop to tone your core, abs, legs, arms, back and butt by re-introducing a playful element into physical fitness.

Osbourne did Hoopnotica to get ready for Oscar night, telling "Self" magazine that hooping was one of her secrets to keeping off the 70 pounds she's lost since 2009.

"I have a Hoopnotica hula hoop," she told the magazine. "I use it every day, and it's made my back and arms stronger, and my waist has gone down 2 inches! On Saturday nights my friends and I put on ridiculous outfits and hula-hoop and dance when everyone else is at 'da club.' We call it #HipHopAnonymous. Adam Lambert is in it. We live in the same building, and random people show up. The next morning you're like, 'Oh, my God, I'm so sore,' but you had the best night ever."

Jackie Hesley, a certified Hoopnotica instructor who learned her moves at the Hoopnotica studio in Venice, Calif., has also lost about 50 pounds in six months.

"It is cardio and strength training because you're using all of your core muscles," Hesley told ABC News. "You tighten up the sides of your body and you tighten up your center or your hips or your legs."

Gabriella Redding started Hoopnotica because hooping seemed fun and healthy to her. After originally weighing 182 pounds, she's lost 50 pounds in a year thanks to exercise.

"You can burn up to 600 calories in an hour, moving your arms in and out and coming up," Redding said.

And Osbourne isn't the only celebrity hooper. Michelle Obama, Catherine Zeta Jones, Jason Mraz and Beyonce also reportedly enjoy the exercise.

Hooping burns an average of 420 calories per hour, which is the equivalent of a cardio-kickbox class.