With rave reviews pouring in for her box office hit Spy, Melissa McCarthy is on her A-game. And to make success even sweeter, the star's rocking a decidedly smaller waistline!

Down a reported 50 pounds this year, the mother-of-two credits a change of mind-set with helping her finally beat the bulge.

melissa mccarthy

September 2011 vs. June 2015.

"I truly stopped worrying about it," the 44-year-old confesses to Life & Style. "I think there's something to kinda loosening up and not being so nervous and rigid about it that, bizarrely, has worked."

Melissa also kick-started her weight loss with workouts to prep for fight scenes in Spy. "The second I knew I was doing the movie, I started training with an amazing martial arts instructor," Melissa shares.

melissa mccarthy
20th Century Fox

Melissa in ‘Spy.’

And the Mike & Molly star has reportedly been following a high-protein diet, "which is effective because it helps rev metabolism, boosts energy and enhances satiety," says Wendy Bazilian, DrPH, RD.

But Melissa doesn't beat herself up if she slips now and then. "It may be the best thing I've ever done," the star tells Life & Style of her new attitude. "I feel amazing!"