James Corden has criticised the exclusion of "chubby" people in films and on TV, saying they "never really fall in love... never have sex".
Speaking on David Tennant's podcast, the TV host added that "certainly no-one ever finds you attractive" on screen if you are a larger size.
He added that those actors are, at best, cast as the "good" and funny friend of someone who is attractive.
Corden said being excluded from roles spurred him on to write Gavin & Stacey.
He said: "I had no idea if I'd be able to write. It came about because I had done a film with Shane Meadows, I'd done a Mike Leigh film and done Fat Friends on ITV.
"And now I was in this play, which was the play to see [The History Boys]. And I was in this play with seven other boys who were at a similar age and a similar place in our careers.
"And pretty much every day, three or four of these boys would come in with this massive film script under their arm."
He was offered "the hottest script" along with two other History Boys actors, he explained.
"They both got sent the script [for the lead roles] and I got sent just two pages to play a newsagent at the start of this film.
"I really felt like people were going, 'We think you're quite good. It's just because of what you look like.'
"If you only watch television or films, if an alien came back and they had to take a reading on planet Earth by just watching films or TV, they would imagine that if you are chubby or fat or big, you never really fall in love, you never have sex.
"Certainly no-one really ever finds you attractive. You will be good friends with people who are attractive and often will be a great sense of comfort to them and perhaps chip in with the odd joke every now and again."
He added: "It felt like if the world of entertainment was a big banquet table, people are like, 'There isn't a seat for you here.'
"I was like, 'If that's not going to happen then I'm going to try to make something happen for myself'."
Corden went on to write and star in the hit BBC sitcom Gavin & Stacey with Ruth Jones and now hosts The Late Late Show on CBS.
He has previously touched on his frustrations on the way Hollywood represents larger people.
In an interview with Rolling Stone magazine in 2016, he said: "I could never understand when I watched romantic comedies. The notion that for some reason unattractive or heavy people don't fall in love.
"If they do, it's in some odd, kooky, roundabout way - and it's not. It's exactly the same."