Just because a person wants to eat, it doesn't mean he or she is truly hungry. Hunger is caused when blood vessels lack nutritive materials and a message is sent to the hunger center of the brain. The brain tells the stomach and intestines to become more active; that's why a hungry person hears his or her stomach rumble. A calm individual can live longer without food while, an excitable person uses up the food they have stored quicker.
When a person is hungry, he or she doesn't crave just one food in particular. Bodies just want nourishment. Our appetites ensure that we eat more than one food in particular, because eating only one food would be unhealthy. It would also get quite boring to eat the same thing every day.
Consuming food isn't just about chewing and swallowing. Once food has been chewed and swallowed, the rest of the work occurs in the stomach. Hydrochloric acid and pepsin are two secretions, or juices from the stomach wall, that aid digestion. Starches continue to break down until the food is very acidic.
Food is more than just something people consume when they are hungry. Their whole lives revolve around it. Eating is one of the most important parts of a human's well being.
Without a healthy digestive system, it would be impossible to eat food. People would most likely have to eat through a feeding bag connected to their stomachs, which would make eating painful and maybe even embarrassing. So, next time you pick up a piece of asparagus, remember you're not just eating because you're hungry – you're eating to survive!
[Source: The Big Book of Tell Me Why]