People are forced to eat more than they should primarily because of hunger pangs.
I am not sure this is true in contemporary West. I suspect that a lot of overeating happens because of social cues ("I'm at a dinner party so I should eat even though I'm not hungry") and for purely psychological reasons -- from boredom and activity displacement ("I'd like to procrastinate a bit, let me go and have a snack") to hedonics ("Sugar boosts make me feel better, yay sugar!"). None of that is actually hunger.
Perhaps that's also a reason, but the role of insulin / leptin resistance in causing hunger pangs (contractions of the stomach) in situations when additional food is not actually required is pretty well established.
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