You don't have to be alarmingly thin for the top ribs to show. If someone takes my pic from the front, all I have to do is arch my back to get my top 2 or 3 ribs to show. I'm 5'4" and 112. Thin but nowhere near scary thin. Same story when I was 117.

I think the fatties you're looking at on the low-rent Florida sites are skewing your body image ideas.
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"What I do know is that if Karen Carpenter and Mama Cass Elliot had shared that sandwich they'd both be alive today." -Michael K