What is the difference between hunger and appetite?

It is very easy to find the correct answer to the question, How much shall I eat? You are never to eat until you have an earned hunger, and you are to stop eating the instant you BEGIN to feel that your hunger is abating. Never gorge yourself; never eat to repletion. When you begin to feel that your hunger is satisfied, know that you have enough; for until you have enough, you will continue to feel the sensation of hunger. If you eat as directed in the last chapter, it is probable that you will begin to feel satisfied before you have taken half your usual amount; but stop there, all the same. No matter how delightfully attractive the dessert, or how tempting the pie or pudding, do not eat a mouthful of it if you find that your hunger has been in the least degree assuaged by the other foods you have taken.

Whatever you eat after your hunger begins to abate is taken to gratify taste and appetite, not hunger and is not called for by nature at all. It is therefore excess; mere debauchery, and it cannot fail to work mischief.