How do you treat an eating disorder that has lasted 20yr?

Eating disorder. It depends on the eating disorder. Emotional and physical support are necessary. Although a pt has survived 20 years does not mean they still aren't severely harmed or could potentially die. A thorough history and physical w/ an expert physician who treats these patents is a must. Psychotherapy, perhaps antidepressants, poss other meds please note that I don't believe this is "just" a mental disease.
Eating disorder Tx. Chronic eating disorders are best treated thru cognitive behavioral therapy with experienced phd that is familiar with eating do's.