Briefly, I'll try. An aspect of the symptoms of an eating disorder is the desire to be perfect. Often the person struggles to maintain an image of perfection, even to the point of lying and using other forms of subterfuge to convey the perfect image. Also, people in the eating disordered person's life may come to expect an impossibly high standard to be maintained. Then we've got a painful situation where people are trying to live up to what they believe are standards in other people's minds as well as their own.
Nobody knows anybody, really.
The false presentation is a terrible burden to carry. It's a set up for disappointment and painful disillusionment. That's the 64,000 dollar question. I can give you a list of possibilities. These possibilities are indeed factors in people becoming compulsive overeaters.