There's a great article on the skinny-fat paradox here, from CrossFit SouthBay.

This is a tough one for people to wrap their minds around, and I see it effecting females more often due to the emphasis on being small/skinny/petite.

There is a difference between being skinny and being healthy. I see plenty of people that are skinny, a size 4, and couldn't survive the elevator being out of service.