I guess it would depend on what "withholding" meant and what "food", etc. I could see not giving treats/"dessert", favorite foods, maybe "terminating" dinner or whatever because a child would not behave appropriately and had been duly warned what would happen if they did not sit and eat properly, etc. I don't think it is about the food, the child is not going hungry or being threatened with that but it does not seem that much different from rewarding learning to become potty trained with M&Ms :-) or going out for ice cream on one's birthday, etc. Food is woven into our life and is a "social" event and is a good socializing element, can help children learn how to give and receive, is a good platform for thought and conversation, in my view. That many now seem so much busier and grab food "on the go" so often and eat alone, gulping the food down as fast as they can, not even tasting it, etc. is a greater "crime" to me than working with food in the opposite direction, to teach a child to "value" it and the relationships one has.