06/30/2009 AT 04:50 PM EDT
isn't afraid to bare it all – at least not on set.
"If I can't flaunt it at 20, come on!" Panettiere said while promoting her new film I Love You, Beth Cooper
, in theaters July 10. "I mean I might as well show it now."
In the movie, Panettiere plays unattainable Beth Cooper, a high school cheerleader and the object of dorky Denis Cooverman's (played by Paul Rust) affection, and in one locker room scene, the actress drops her towel.
"It didn't bother me much," Panettiere said of shooting the "reveal." "I think when the person who's doing it gets all uncomfortable and shy, then it's other people around who get more uncomfortable because they're uncomfortable. I mean I was fine – everyone was really professional."
Even so, Panettiere said she still deals with body image issues.
"The older I get, the more comfortable I get with it," she added, "but I still have my days where I don't feel great ... and I'm having my fat day where I have to put something baggy on and sweatpants. Or just with the way people perceive me. I have plenty of insecurities."
But she tries to maintain a healthy lifestyle, she said. "I have the body that I have and that's not going to change," she said. "I try to stay as healthy as I can."
Panettiere now is gearing up for season four of Heroes
, which returns to NBC in late September.
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