Your body has plenty of stored energy. Your body also feels pretty amazing after fasting as well, you should try it some time. I normally fast every month or two for 2-5 days or so. Also, with certain types of illness, fasting can be beneficial towards speeding up your recovery. "Certain health shakes" are for the most part, a complete crock.
What I meant about "certain health shakes" was food broken down into a slushie-sort form, to make your it easy for your body to break down and doesn't leav all kinds of shit behind. And they're a crock just as much as fasting.
Of course your body has fat stores - but it needs some energy to break them down. If you want to take care of them, just eat less, so your body will have some mininum amount of energy and still break down all your stored energy (which I don't get why you'd want to do that, unless you're overweight).
And I have fasted, and felt it was a huge waste of time. The great feeling you have can just as well be psychological as anything else. I mean, for fucks sake, you haven't eaten for an entire day - of course you'll feel great when you're full. The same way that some people who have migraines usually feel some kind of euphoric feeling when their attack is over - doesn't mean it's good for you.
I know that there are many different views about this whole thing, but doesn't it just sound more logical that starving yourself for a day and depriving your body of it's fuel is not good for you? It may eventually end up that way, but it just doesn't make sense.