The singer made the comments during an On the Air With Ryan Seacrest interview to promote the upcoming release of her seventh studio album.
"He's definitely ripped," Spears admitted. "He just got on this health kick."
Seacrest, who has been friends with Trawick for many years, joked with Spears that her boyfriend hadn't always been so aesthetically appealing.
"I don't want to make you uncomfortable, but I knew [Jason] when he was hairy and pudgy," the American Idol host laughed. "But now he's fit and he's got zero percent body fat."
Spears also revealed some of her own fitness secrets, claiming that it is natural to have a love-hate relationship with your personal trainer.
"I'm on the treadmill for 30 minutes and we do a lot of cardio and running, he kicks my butt," the singer said. "You pay to hate your trainer, it's so odd."
Spears' new album Femme Fatale is due to be released on March 29.