Honestly I don't think anything good or bad willcome from it (other than Mary Kate's recovery or her lack thereof...it could be either).
I don't think this will affect her career. I also don't think it will change the medias body image ideas, nor will it the general publics perception of body image.
To me, people will see it as something that happened. Soon enough we'l forget about this and move on to bigger news...like J.Lo's baby and subsequent divorce.
