Actually, it's not tricky at all. Check it out.
When you look at the women you love to look at, you think they're beautiful
Cut and paste that to BBW and you've got it
If a BBW lover looked at slim models and made a tour saying "Check out our latest bulimic stick figures! They hawk up every meal just so you can damn near see their bones!" You'd probably say WTF?? Thats sick!
Your ads just have to insert themselves into the dialogue that is taking place in the surfers mind. Perspective!