In a recent interview with British magazine The Closer, Katy's trainer Harley Pasternak revealed how he was whipping her into shape.
"To stay toned and fit, but retain her curves, Katy aims to exercise five days a week, doing short, high-intensity workouts - including lunges and hip thrusts," he explained. "These tone, as well as boost her metabolism, and can be done anywhere."
Apparently, they also did a diet overhaul, cutting out alcohol and fatty foods. As not fun as that sounds, it totally worked and Katy looks absolutely incredible.
Wonder what her ex, John Mayer is thinking right about now?
Katy is currently in the midst of her Prismatic World Tour, where she'll be showing off that incredible body on stages all across the globe through March 2015.