Hunger is far more complicated than "my weight is below normal for my height, I should eat now." It's not some sort of correction mechanism that turns on and off to make your weight go up and down.
On a first approximation, you feel hungry because your stomach is empty and/or your blood sugar is low. People can drink water or eat lettuce to fill up their stomachs, and that works a little. Often, if you eat something very high in sugar, not mediated by anything slower to digest, you will be even hungrier afterwards because of your body's insulin response. The web is full of "foods that make you hungry", "what to do instead of eating when you're hungry" and such like, some of which have a grain of truth in them, and that certainly demonstrate how complicated hunger is in humans.
Studies have been done showing that people can get hungry for a variety of reasons that have nothing to do with their current weight. Here's a review of various papers relating to insulin levels and cognitive factors such as looking at or thinking about food.