Answer: After a physical activity, we take deep breathes and inhale more oxygen. As a result, more oxygen is supplied to our cells and the process of breakdown of food speeds up. Due to this, more energy is released and we tend to feel hungry. Hunger is partly controlled by a part of your brain called the hypothalamus, your blood sugar (glucose) level, how empty your stomach and intestines are, and certain hormone levels in your body. Fullness is a feeling of being satisfied. Your stomach tells your brain that it is full.When a person eats, nerve receptors inside the stomach sense when the stomach is full. These receptors then send signals to the brain, which the brain interprets as a sensation of fullness.