The diva was back. As Mariah Carey took the stage in a series of glittering, body-hugging gowns at The Colosseum at Caesars Palace in Las Vegas for her holiday show, All I Want for Christmas Is You, on Dec. 14, audience members gasped. “Oh my God, she looks incredible!” one fan exclaimed, while another marveled, “She looks so good!”

Mariah has shed a lot of weight — and a lot of personal baggage. “She’s had one of the hardest years of her life,” a source exclusively tells Life & Style, noting that in the wake of last year’s New Year’s Eve lip-sync debacle and critically panned reality show Mariah’s World, “she hit an all-time low and as a result she gained some pounds.” But in recent months, she’s slimmed down dramatically while readjusting her attitude and her inner circle. “Mariah is closing out the old year on a high note,” says an insider, adding that the singer has lost at least 25 pounds. “She feels like a new woman.”

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Mariah’s vanity is legendary. So the performer, 48, hated seeing photos of herself looking sloppy and bloated over the summer. “Jokes about her weight and memes about her backup dancers [including boyfriend Bryan Tanaka, 34] struggling to lift her were a big motivator,” the insider says. She decided to make some changes. The biggest: giving up booze. At her Vegas show, Mariah — who normally drinks champagne during performances — announced that she was avoiding alcohol, joking that the lifestyle change was “very boring.” But it’s paid off.

Fitness coach Nadia Murdock, founder of Nadia Murdock Fit, tells Life & Style the singer appears to have gone from roughly 175 pounds in mid-September to 150 pounds now. “She’s lost a significant amount of weight in her face and midsection while maintaining her curvy figure,” she says.

Some believe Mariah went under the knife. “She didn’t deny having some kind of weight loss surgery when asked about it,” says a second source. But the first source insists that besides quitting drinking, Mariah slimmed down by dieting and exercising. “She did a master cleanse and went on all liquids for 10 days,” says the source. “She also walked on a treadmill and danced her heart out.”

Bryan’s supported her throughout it all. And her relationship with ex Nick Cannon, 37, father to their twins, Moroccan and Monroe, 6, couldn’t be better. With their help, she’s looking forward to taking her transformation even further. “Mariah is pulling out all the stops to make 2018 her comeback year,” says the insider. “She’s slimmer and happier than she’s been in a long time,” adds the source. “She feels like she is turning her life around.”

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