Ashton Kutcher quit gym for new movie

Ashton Kutcher deliberately stopped working out before filming 'No Strings Attached'.

Although the 33-year-old actor knew he would have to bare all during sex scenes with co-star Natalie Portman in the romantic comedy, he warned director Ivan Reitman that he would let himself go to make his character writer Adam seem more real.

He explained: "I actually stopped working out for this movie. I literally had a conversation with Ivan before I started and I said, 'This guy is a production assistant, aspiring writer. I know a lot of these guys and none of them are particularly fit.' And I just felt like that was necessary for this character.

"I thought making sure that this character was real was really important.

However, the hunk - who is married to actress Demi Moore - believes he may not have toned down his exercise enough because people are still complimenting his body in the film."

He added to BANG Showbiz: "Apparently I didn't let myself go enough because that's all anyone wants to talk about. That and my derriere."

Having his body under scrutiny doesn't faze Ashton, who says he enjoys being naked - although he admitted sex scenes can be awkward, especially for women because film crews are usually predominately male.

He said: "I like having it out! I like being naked! We all come into the world this way. There's very little you can do about it. You are who you are. Doing the scene, it doesn't matter. It's infinitely awkward. You have 40 strangers standing around. I think it's less awkward for guys than girls because I think the crew tends to be slightly more masculine."