One thing my mother taught us is that if you crave something specific to eat, there's a reason to it. Years later, fatties took the idea up to deny that eating fifteen cheeseburgers is too much, but there's a truth within every lie, as no one can be consistently wrong. The truth here is that your body is pretty smart and knows what you need, you only have to learn to listen. So if you are dying for a banana no matter how much you ate, you gotta eat a banana. Chances are you lack kalium or so. Just make sure you differentiate the healthy cravings from the unhealthy, purely psychological ones, like craving chocolate whenever you watch a movie because you always eat chocolate when watching a movie.