The principles of this answer can be applied to other addictive disorders than eating disorders.
Let us suppose there are two people in your head fighting for power:
Sara junior and Sara senior (choose your own name). Sara senior will have
some order in her eating habits but Sara junior only thinks about
immediate satisfaction and completely ignores the consequences. While Sara
senior has decided to stop eating chocolate and buns, Sara junior can
gladly stuff herself with biscuits and chocolate without thinking about
what the future effect will be. Sometimes one is in power and sometimes
the other.
In order to be successful, it is necessary to understand how these two
sides function. Sara junior is strong and often wins in a confrontation.
Sara senior is more cunning and can win by being prudent. For example:
Sara senior travels home from her job by train. There is a kiosk at the
station where she buys chocolate every day, even though she knows that she
shouldn't. One day she decides not to have any money with her when she
goes to work. Sara junior gets angry when she realises there will be no
chocolate but can't do anything about it. When Sara senior comes home she
eats a sensible dinner and is proud that she has outwitted the food
monster inside her.
Sara senior soon becomes so used to not eating chocolate on the way home
that she is able to take money with her without spending it at the kiosk.
Sara senior has become stronger and can overcome Sara junior.
John is another example. He used to wake up every night and eat without
restraint. However sensibly he had eaten during the day, he destroys the
good effects by eating at night. If he had no food at home, he went out
and bought some. His neighbour Britt learned about this and promised to
help him. When John had eaten his supper, he locked the kitchen door and
pushed the key and his wallet through Britt's letter box. In the morning
she pushed it back through John letter box. During the day John had good
control over his eating and after some months he could manage without
Britt's help. He had become used to not eating excessively at night. Of
course, the first nights were not easy, but he gradually got used to
listening to the radio if he couldn't sleep.
It was extremely tempting for both Sara and John to give way to the
impulse to eat excessively but they felt much better psychologically and
physically when they had become used to
regular, nutritious meals instead of eating in order to reduce anxiety.