I am lucky in that I work with some very smart people. Scuttlebutt around the office is that the human sense of thirst is particularly indistinct, or poor. What they say is that sometimes you feel hungry, you are actually thirsty, your body just isn't good at distinguishing it.
So, each time you are hungry, drink a glass of water (6 ounces should do) and wait 15 minutes. If you are still hungry, then eat.