The Scottish actor - who turns 40 on March 31 - has decided to keep his clothes on in all his future roles because he thinks he is getting too old to strip off on screen.
He said: "I`m getting older and the actresses stay younger.
"I don`t want to become Clint Eastwood, where his love interest is 50 years younger than him. You never want female co-stars to feel like you`re taking advantage of the situation.
"Anyhow, sex scenes are terribly exposing and rarely of any use in learning about character. Directors are always pushing you in these really strange ways, saying, `Let`s just see where it goes.`
"I like it when the sex is more choreographed. It`s somehow easier to do."
Ewan has agreed to full-frontal nudity in several movies, including `Trainspotting`, `Velvet Goldmine` and `The Pillow Book`, and insists he has never had a problem with baring all for the cameras.
The `I Love You Phillip Morris` star - who is married to French production designer Eve Mavrakis, with whom he has three daughters Clara, five, nine-year-old Esther, and adopted Jamiyan, who is also nine - added: "It`s all about life. We`re naked at the end of the day and we`re sometimes naked in the middle of the day if we`re lucky. It`s just part of life. It may seem like I`m obsessed with sex, but it`s actually the opposite."