That wouldn't make any difference anyway, it's the wrong approach.
Look at all the ridiculous threads where posters fall over themselves to show how witty they are and need to eat ridiculous portions of food every 2 hours, and the even more ridiculous "fat shaming" expression to disagree with any common sense point related to weight.
We need over-eating and bad food to become unfashionable, not by banning adverts. celebs are skinny, but it has no effect on the street, we need to reverse the trend.