Anorexia. It should be listed in DSM-4 as a Delusional Disorder, but they call it an 'Eating Disorder'. Why.?

Because it is largely centered around food and eating. Yes there is a distorted body image but it extends mostly to ones self. A hallucination is not as subjective and clouds all reality not just aspects relating to ones self/body. Also, when one is experiencing a hallucination there are biological changes to the body that can be registered in an eating disorder what is noticed is more of a thought pattern that can be addressed but using theutic methods more suited to behavior change and reduction rather than anti-psychotics.