One is always portrayed as bad, and other is portrayed as good and/or normal by the people who promote it. I don't think there's anybody here who thinks that girl is attractively built. Yet the fashion industry continues to find girls like that to model their clothes, even though nobody in this country (thank god) really looks like that. Because of that, you now get girls who think that's an ideal and want to shrink themselves down to the proportions of a Treblinka survivor.
Nobody has to be told that being a fat-fuck isn't attractive. As we see here, plenty of girls need to be told that being too scrawny is equally unattractive.