There is a book I have been reading but now I cant think of the name of it. Basically it says that we should ask God what he wants us to weigh. He will let us know what number he wants us to be at and then we need to pray and ask him how many calories to eat a day and he will answer that as well.
The book explains how we should diet for God and no one else b/c we dont want to let God down and we want to succeed for him. It also states that when tempted we need to pray about the situation and God will bring us through it.

When you ask God what you should weigh your supposed to have some christian friends pray as well for you and see if they get the same number that you did. Sometimes what we think is God really is us.