yes, there are some who are naturally very thin, but there is a huge amount of pressure to maintain a lower than ideal weight/stay toned etc. reputable agencies are more careful but its really the designers who have an issue with a size 8 rather than a 4, and then you have the whole airbrush nonsense. the models in the link look great though.
that said, I think that we are, as a whole too quick to accept overweight as the norm. to the point where it is acceptable to tell a slim woman to "eat more pies"/comment on their size/what they eat ("where do you put it all?") and dismiss them as unhealthy/anorexic/unnaturally skinny. however, I dont think its acceptable to judge or mock anyone based on their size. I loathe the "real women" tag and the assumption that a size 16 is sexier than a size 6. And its women who do it. to make themselves feel better at the expense of other women.
but, Im sorry for my first post. I am ultra-sensitive about the use of "anorexic" because its such a serious, awful, soul-destroying disorder. and it seems to be used rather flippantly.