I know a bulimic person. How can I help him/her?

First, it is important that you know how to distinguish an healthy eating behavior from a problematic one: it could be that this person follows a very strict diet, but if he/she continues his/her life in a natural way, not necessarily suffering from a disorder. If someone has an obsessive thought than the food, then he/she might suffer from bulimia and may need to be helped.