Can a person be anorexic without any physical symptoms other than thinness?

Whenever I hear about anorexia, I hear about how your hair will become lackluster and brittle and fall out, or you’ll get yellow skin and you’ll loose muscle mass. But can someone be anorexic without any of those symptoms? What about when you’re post-menopausal and it would be hard to tell if your hair wasn’t shiny and your bones weren’t strong because of anorexia, or just because you’re getting older?