Ever notice how your stomach says "I'm full" but your brain says "I want more"? That battle between true hunger and mere appetite has challenged humans for millennia.

The ancient Greeks were onto something here. Socrates taught his students that food should satisfy hunger, not feed your cravings for sophisticated tastes. He pointed to Odysseus, who resisted the sorceress Circe's magic because he ate moderately, while his feast-loving crew were transformed into pigs. (Not subtle, those Greek metaphors.)

But what exactly is the difference between hunger and appetite? They're not the same thing.