I would assume you don't expect to make it the only topic of interest though.
Think I found a new rule of thumb for 'way too skinny', at least for women. If you can see ribs
between the boobs, that's just gross.
Keira Knightley's been in the news for this so I'll use her as an example:
Not gross ->
http://images.eonline.com/eol_images...ira.091906.jpg
Gross ->
http://www.americansuperstarmag.com/...knightley1.jpg
Actually, ribs showing when your arms aren't above your head is still within the 'eat a sandwich' range.
Before she decided that her body was capable of running entirely on oxygen without the need for all that messy food she was, in my book, far and away the most attractive woman in Hollywood. Now she's a case study.