I've read before that you can totally do it, but you need to eat a lot of vitamins and other things that aren't stored in your fat cells and that you usually get through food, to make sure you survive without significant damage.

If, like this guy, you have doctors monitoring you, you'll be okay.

If you just try to go about it without eating, you'll eventually end up with a deficiency in something or other, and have health problems until you eat whatever nutrient it is your missing again.