Now that he's 55, it's getting harder and harder to bounce back after these long, demanding projects. "His body is breaking and cracking under the pressure, and he knows it," said an insider. The Oscar winner revealed that "getting jacked in [his] 50s" required a "complete lifestyle change," including cutting way back on calories while ramping up his fitness routine. "It's been this way for Matt's entire career, where there's almost no limit to the physical punishment and stress he'll endure for a movie where he's one of the leads," a source said. "He's put himself through hell again and again, between all the fighting he did in the Bourne movies to the extremes of weight loss and weight gain he's gone through on projects like Courage Under Fire or The Informant," the source added.