Gerard Butler explains his fluctuating body mass.

If you have been worried about Gerard Butlers fluctuating body mass there is no need to worry. Gerard has been preparing himself for a movie role.

“I’m prepping for a surf movie,” Butler, 41, told PEOPLE at a Machine Gun Preacher screening Tuesday in New York. “So I’m surfing every day for Mavericks.”

Not to worry, fans of his physique for 300 can have hope that the action star will get his 6’2″ self back to that film’s 197 lbs. of muscle. “If the script was good, I would do it,” Butler says of a rumored sequel – and necessary bulk-up. “I’ve got to feel that there’s a real reason to go there, to do a second one, because I loved the first.”