The 127 Hours actor - who is to host this year's Oscars ceremony alongside Anne Hathaway - says appearing in a raunchy home movie gave him more respect for porn stars because he knows from personal experience how hard it is.
Speaking in a discussion held by Newsweek magazine for potential Oscar-nominees, James said: "I think if anybody who has made a home sex tape knows, what feels best doesn't always look best. I remember when I was 19 doing that, and then watching it back and thinking, 'Oh, that looks horrible.' You have a lot of respect for those actors in pornography, because they are really not just doing it, they're really selling it."
This is not the first time James has been so open about his personal life.
Last year he revealed he masturbates "four or five times a day" because he is alone a lot.
He said: "I spend a fair amount of time alone, especially when I travel for work or whatever, but I'm in hotels a lot for a lot of my life. So, when I'm alone, I do masturbate a lot. I don't know why. It's like you have those days where it's just like, I have a ton of writing to do, or a ton of reading to do, and you're just like, OK, I'm going to be on the couch all day or in bed all day just doing that. I tend to have a four- or five-time day."