Yes, I agree, talk about health is key, as is a focus away from body image and on being a good person. But the fact is, we really don't want our children to be fat -- not only because it is unhealthy, but because in our uber competitive world, a fat person is less likely to be hired, or to be asked on a date -- and yes, all of that matters. Unfortunately, what's outside matters too.
My son has a rule of sevens to overcome sadness: seven hours, seven days and seven weeks. He allows himself to get sad or angry for a certain period of time. For him, it can be seven hours, seven days or seven weeks. When the time is up, he tells himself that he needs to move on and stops dwelling on situations that he can no longer change.