The portion of your brain most closely involved in controlling hunger is the hypothalamus, a part of your brain that also regulates other bodily functions like temperature, thirst, memory, sleep, growth, and more.
One signal the hypothalamus uses to decide whether you need to eat is how distended your stomach is. If your stomach stretches in response to a meal, this information feeds back to your hypothalamus. In response, your hypothalamus gives you that full sensation. If you haven’t eaten in a while and your stomach is empty, the opposite happens. You feel hunger.