I don't remember where I actually read this, but water--good ol' water--was shown to actually have negative calories. Apparently, it takes more energy than the water contains for your body to properly digest it, so you burn a small amount of fat or other energy block. I believe the figure was -4 calories for an eight ounce cup of the stuff. Neato, eh?

I suspect they just label bottled water at zero calories to prevent a mad rush of people obsessed with their weight from picking up crates of bottled water in the hopes of drinking those extra pounds away.