Now that she's lost 50 pounds, Jordin Sparks is looking -- and feeling! -- better than ever.

To celebrate her body makeover, the 22-year-old Sparkle actress posed in a  sexy blue bikini for the cover of Shape magazine's August issue.

"I just wanted to be healthy," she says of her slimdown. "I remember thinking, 'I'm in my prime. I should be happy and fit.' That was the moment I decided that changes needed to be made."

Making those dreams a reality was no easy feat for the season 6 American Idol champ. "I knew I had a long road ahead of me. I was barely working out and my diet was a mess," Sparks says. "I had to address when, what and how much I was eating."

Several months in, Sparks noticed a change in her body. "The weight really started falling off and I could see my muscles," she tells Shape. "It was awesome!"

The "Battlefield" singer's new film, Sparkle -- costarring the late Whitney Houston -- is in theaters August 17.