Have you read Wheat Belly ? Wheat is addictive.
Have you read Fat Chance ? Sugar is addictive.

Both light up the same areas of the brain that cocaine, heroin and other drugs do.

Why is it so difficult to stop? Because they are addictive. Only you can stop and only when you are convinced that you are addicted and you no longer want to be controlled by them. Seriously, some research might give you the insight you need to do this. Good luck!