Ludi Boeken has said he didn't find it tough to keep up with Brad Pitt in World War Z's action scenes as he's in such great shape.
The actor appears in the zombie film with Brad but said although the action scenes were tough, he wasn't intimidated by the star.
He said: "It was tough work, especially in my scenes, we kept on running up and down with Brad... Costume gave me a winter jacket and it was 40 degrees and I was sweating and sweating. I lost a lot of weight which was probably a good thing because I could do with losing weight."
Asked whether he trained to keep up with Brad, Ludi said: "No, he had to get into a training regime to keep up with me... He's in great shape but I was in good shape too, surprisingly."
Ludi, who is usually the other side of the camera as a producer and director, said having an acting role took some getting used to.
He said: "It was so scary, it was more scary than actually the zombies were. At the beginning I thought 'Oh, my God'. I've done it a few times but never on a big movie like that with great big stars and important directors, so this is quite something.
"At the beginning I was really nervous, but that evaporated quickly. You get used to it."
World War Z is released in cinemas on June 21.