The system of dieting = failure
When you go on a diet, your need to assert your autonomy overrides and is stronger than your need to lose weight. This has to do with the internal violation that dieting represents. As an adult, you set up boundaries about what to think, what to believe in, and what to eat... In the world of dieting, the external rules of the diet crosses over into the boundary that protects all of your personal eating wisdom. The simple act of stepping across your personal, psychological boundary can trigger so many thoughts and feelings and actions of rebellion. You’re being told what to do, and you react against that. There is absolutely nothing wrong with you when you’ve ‘failed’ at a diet. Rest assured, you’re actually psychologically healthy.