If your bigorexic friend asks for your help is important to don’t improvise expert, do not follow the advice of others, but contact a doctor or specialized centers.
First, it is important to distinguish an healthy eating behavior from a problematic one. Someone who follows a very strict diet, but continues his life in a natural way, it is not said that suffers from a disorder. If someone has an obsessive thought with respect to food and destroys any form of pleasure, then that person might need your help.