Sorry about the baiting title. Anorexia is a mental illness and blame is probably the least useful thing in every case, although it is neck and neck with denial. I watched this PSA for the first time today. It is pretty extreme. It is pretty provocative. It is not pretty.
I think that the first line of defense should be regularly eating meals together with any child that you feel may be at risk. If reasonable efforts to encourage a healthy relationship with food are met with resistance and acting out, get professional help sooner rather than later.