Yeah yeah! We all know that, it has been said / referred to upthread.
But it as not always been associated with the unhealthy body image from the world of fashion Kate Moss read it in a book, a collection of short stories by Elsa Berg, that pondered and celebrated small acts of 'feminist rebellion', published the year before Moss said it.
I'd lay good money that she, Moss, had read the book, or heard the saying in much the same way Berg had... all over the place, wherever you see a fat woman you will hear a woman try a version of that to resist the lure of a favourite food, an extra mouthful.
Using flippant mottoes to try and lose weight it not the same as promoting anorexia. To suggest it is remains the height/weight of hubris as it consigns all the complexities of eating disorders to simplistic nonsense.