Try "replacement therapy." Anytime you have the urge to snack, instead of giving into that urge, replace it with a healthier or more desirable action. Obviously, make sure you're eating enough to keep yourself satisfied. You may have created a habit out of overeating, so this should help to replace the habit if done diligently. I had a friend who quit smoking cigarettes via this method. He alleged that anytime he got a craving for a cigarette, he would just drop down and do as many push-ups as he could manage and claimed that by the time he was done with the push-ups he forgot about his craving. It's worth a shot!