Last year I went like 5 days without eating or drinking anything. I know it's not that many days but I really did stop feeling hungry. A teacher of mine also tried not eating for 2 weeks and his experience was similar to mine, you get very hungry at first, it goes away and then you are full of energy. He said he felt fine for the 2 weeks he didn't eat, I however started having a very small headache by the 5th day (although that was probably because of dehydration). Remember, in the past, food was scarce. Our body is adapted to not eating food.
Also I guess it would be painful at some point, your body would start eating itself in order to survive (Muscles and stuff)