Fifth rule - Eat what you really want, precisely when you want, and stop when you're full.

Many animals have the good sense to eat what their body needs and there's plenty of research on animal seeking out particular plants when ill. There's also plenty of research that human sense of smell is really very sensitive, one would imagine quite sensitive enough to make the same decisions (your sense of taste of flavours is primarily driven by your sense of smell).

So my pet theory is that you, if you think about what you actually really want to eat (barring additictions/daft things), can probably figure out what's best for you.

Another thing to think about is the idea that you should finish what's on your plate - this particular piece of morality/good manners is one you should get out of if you don't want to put on too much weight. The trick is always to stop when you're pretty much full. What's more, what determines whether you feel full is your stomach - and this is a very stretchy thing. So if you stuff yourself at one meal, it will take more at your next meal than it otherwise would to feel full.