I agree with what you are saying, but I suspect that it would be confusing if the image of an overweight person doesn't match expectations? Here is that BBC graphic again with someone borderline BMI obese...
(http://i245.photobucket.com/albums/gg53/shyumu/bbc_zps9b18fcf7.jpg) (http://s245.photobucket.com/user/shyumu/media/bbc_zps9b18fcf7.jpg.html)
And in the meantime, plenty of people have been fighting for the fashion industry to be more representative of the population, to help reduce the focus on the size 0 culture. I don't know what the answer is - but I agree that I :facepalm: when I saw this article too.