I'm not sure about some of the conclusions that article comes to, or rather it's my opinion that they got it backwards. They're implying that it's okay for black/hispanic women to be curvier because they themselves say it's okay, whereas we poor white girls are just so insecure that we can't make that happen for us.
I think it's more the other way around. More white girls are insecure BECAUSE there's less wiggle (or jiggle, heh) room for us. Black/hispanic girls don't get as much crap for having curves, so of course they're going to be less insecure on the whole; they've got more support (especially from the men) saying hey, it's okay, you look hot that way! One group has every single fashion mag staring them down going "SIZE ZEROOOOOO! SIZE ZEROOOO!" while the other two groups get more of "Well, you SHOULD be a size zero, but gosh, you're just so exotic that it's okay that you're not! Grrr, sexy mama!"
(Not that the whole "Latina = exotic slut" and "Black = wild jungle bitch from Africa" stereotypes are any less offensive than the meek-and-tiny-white-girl, but strictly body-type-wise, y'all generally get less pressure than we do to go all Auschwitz.)
(Although if ever there were a woman who could totally rock the "wild jungle bitch from Africa" stereotype and make it her slave, oh Grace Jones, you were it)