The most important thing about cosplay is the costume and a fan's devotion to the character. It's got nothing to do with body shape. And not all cosplayers are fat... that's such a stupid statement.
I went to london expo, there were lots of really good cosplayers. While, yes, some of them were fat and some had clearly made no effort and just bought one online, most of them had made their own costumes and were not obese in anyway... i mean, did you see the Sakura one (Tsubasa Chronicles) ? She was so skinny and her costume was amazing! I can't remember what the one walking around with her looked like, but her costume was great too! Those two would've been worthy of tv. The Sailor Moon and ... the one with the top hat.. (I haven't watched Sailor Moon) were awesome, the Ed pair walking around were as well and that's only a few of the amazing cosplayers. There are some really good cosplayers out there. Don't just assume they're all obese and dressed as Naruto characters.
I'm going to Amecon and i'm cosplaying each day and the ball. I started my costumes last month and me and my friend are working really hard. I wouldn't consider either of us as obese. We're like size 10.
Besides, who cares if non-anime fans think that all anime fans cosplay. Why should that stop people cosplaying on TV? Most non-anime fans think that anyway. Why not show them how amazing the costumes can be instead.