Well it turns out the 31-year-old pop star has been on a fitness kick to get her physique summer-ready.
"She's looking so great because she has been on a total fitness and workout kick recently," a source tells E!. "She's all about it."
"She's been feeling really motivated and happy and it shows," the source added.
Perhaps Spears has also been motivated to hit the gym lately because we'll soon be seeing her gracing the pages of Shape magazine.
"@Shape_Magazine Thanks for the great photo shoot today!" the former X Factor judge tweeted last week along with a photo of her nails being painted. "It was fun to get all dolled up for the cover!"
Looking good, Brit!
—Reporting by Melanie Bromley