Well, when you get really fat, and lose all of your shame. You become a mentally disabled person like her, and then you need food to stay out of 'Starvashun' mode. In all seriousness it is probably: * Food was used as a coping mechanism because she is so shitty, eventually she became fat from the food No shit and became even shittier so more food is needed to keep her happy * Long story short, notice how if you put your hands on something warm it feels warm but that warm feeling gradually disappears? Essentially nerves adapt to stimuli, this is theorized to happen in the brain as well where the brain adapts to high blood sugar and if the blood sugar returns to normal the person feels as if they are hungry and will eat.