What would be the point of having an *average* looking girl on the cover of a glamorous magazine? Who's gonna care? Who's even going to look at the cover? What would be the point of being so average and unoffensive for them? Would that really sell more magazines?
Understand that mag editors just want something to catch people's attention or to generate buzz.
I seriously doubt all the girls would all of a sudden want to be fat and cover themselves with tattoos because of this particular cover.
Perhaps we only need to worry if someday we end up having bunch of fat-pride parades or something like that. IMHO, it's perfectly okay to be fat and be confident of yourself. If you just have the fat genes or perhaps certain medical conditions make you fatter than average population, so be it. However, if you know you are over-eating and lazy and not looking after yourself, there's really nothing to be proud of by being lazy and careless like that.
Now, with that said, we really don't need to be that judgmental about other people's weight. Just make sure we ourselves are within healthy ranges and don't end up becoming a weight extremist... not too thin and not too fat! I know I'll never become a glamorous girl and end up on the cover of that magazine so I'm not going bother...