I've seen it before but only an episode or two. I remember someone being addicted to eating chalk and that was weird enough to me (although I've heard of people wanting to eat weird things like that because of some sort of nutrient deficiency. It is amazing how addictions or neurosis develop and end up manifesting themselves in the ways they do.
I am not sure I have seen that show, but I have mentioned on this forum before about the strange compulsions/addictions people seem to have. These could include such things as eating chalk, soap, small stones, and almost anything. Apparently they include the things you mention as well. It seems like something must be missing from their diet, and also maybe they are addicted to doing something that is "not right" too. I don't know...humans are certainly odd at times!