Gerard Butler, who packed on some pounds after “300,” is hitting the gym hard to get back in shape, but he doesn’t want anyone to know.

“He’s so embarrassed that his six-pack abs have gone, he works out wearing a baseball cap and sunglasses,” gushed our spy.

“Can you imagine the ladies’ response when they think they scored a Spartan warrior but instead see that gut! He joined a private gym in Chelsea, Peak Performance, that’s so discreet, it’s on the eighth floor and strictly limited to approved members” — one of whom ratted Butler out.

Source, Bauer-Griffin