Right, I was thinking about this earlier today, and discussed it with some friends. I'm not English and despite being what I consider average, I'm being called tiny or skinny all the time. Some told me I was skinny and should put some weight on, but the fact is at 5"7 and healthy 8/10, I just see myself as normal and nothing like skinny nor small (nor fat or big or anything). What's funny is that my mum sees me as being "massive" and I'm indeed slightly more on the bigger side than on the tiny side where I live.
So yeah, I was wondering how cultural standards could make such a difference?