Campfield (et al. 1996) and van Litalie (1990) have developed a theory promptly titled the "glucostatic theory". This theory states that, "when our blood glucose levels drop, hunger creates a drive to eat to restore the proper level of glucose". This theory should be changed to law, especially in the medical field. Type 1 Diabetics, or juvenile diabetics, know too well what happens when your glucose level falls below the normal rage. You turn into an animal seeking anything that is made with sugar or anything that is made mostly out of carbohydrates. Knowing from personal experience, your brain tells you to eat excess amounts of sugar and carbohydrates in order to raise your blood glucose back within the normal range. It sucks too, because it personally wakes me in the middle of the night, blood glucose level is at, like, 50 (when it should be at 100-130), my vision is blurred, my arms and legs feel like Jell-O and I have this animalistic drive to eat everything in my fridge. This provided link gives some indication of what it feels like to have a low blood sugar:
Everyone experiences a low blood sugar differently, but this theory is very real, and shouldn't be taken lightly.
(Sorry if the link doesn't work correctly. I was having technical difficulties all night.)