The sensation of fullness is set in motion as food moves from your mouth down your esophagus. Once it hits your stomach it gradually fills the space, that causes the surrounding muscular wall to stretch, expanding slowly like a balloon, a multitude of nerves wrapped intricately around the stomach wall sense the stretching. They communicate with the vagus nerve, up to the brainstem and hypothalamus. The main parts of the brain that control food intake. But that's just one input your brain uses to sense fullness.
After all, if you fill your stomach with water, you won't feel full for long. Your brain also takes into account chemical messengers in the form of hormones produced by endocrine cells throughout your digestive system. These respond to the presence of specific nutrients in your gut and bloodstream, which gradually increase as you digest your food.
As the hormones seep out, they’re swept up by the blood and eventually reach the hypothalamus in the brain. Over 20 gastrointestinal hormones are involved in moderating our appetites. One example is the cholecystokinin, which is produced in response to food by the cells in the upper small bowel. When it reaches the hypothalamus it causes a reduction in the feeling of reward you get when eating food. When that occurs the sense of being satiated starts to sink in and you stop eating.
The sensation of fullness is set in motion as food moves from human mouth down the esophagus and the sense is communicated with the vagus nerve, up to the brainstem and hypothalamus. Your brain also takes into account chemical messengers in the form of hormones produced by endocrine cells from digestive system. These respond to the presence of specific nutrients in your gut and bloodstream, which gradually increase as one digest food.
