Britney Spears dropped 12 pounds after unflattering photos from the "Pretty Girls" video featuring Iggy Azalea music video set surfaced.

According to OK! Magazine, Brit used the photos as motivation for her workout plan after being "horrified" by them.

"It was a big wake-up call and she's been religiously getting back into shape," a source tells the magazine.

Daily Express tweeted a photo of Britney on the set back in April where her stomach nearly rolled over her jeans when she sat in a truck next to Iggy.

Britney Spears wears unflattering leopard print outfit to shoot 80s video with Iggy Azalea https://t.co/gyB5ZgHJbS pic.twitter.com/ZRjun54jHU

- Daily Express (@Daily_Express) April 9, 2015

After the unaltered photos were leaked in April, the "Piece of Me" singer went on a crash diet. According to the source, Brit complained about how she felt the "biggest she's ever been" and that "she was in tears over how much she'd let herself go."

Meanwhile, the "Pretty Girls" video flopped because of poor advertising. Soon after the video collaboration, the two divas got into a battle on Twitter.

"Can't wait to get back to Vegas. So thankful I have shows for the rest of the year to look forward to... #YouWantAPieceOfMe," Britney tweeted following remarks Iggy made about their collaboration.

Iggy responded to a fan's tweet about the "Pretty Girls" video flopping, hinting it was not as popular because she wasn't the lead person handling everything.

"@rhuancesarr its difficult to send a song up the charts without additional promo and tv performances etc. unfortunately im just featured..." Iggy tweeted.

Britney responded by taking a jab at Iggy's "Great Escape" tour that was canceled. Speculation is she completely canceled the tour because she could not make enough ticket sells.

Meanwhile, Britney has a two-year residency at the Planet Hollywood Resort & Casino in Las Vegas following the footsteps of other famous musicians including Cher, Celine Dion and Mariah Carey.