Hunger begins when certain essential nutritive materials are missing from the blood. When the blood vessels lack this material, a message is sent to part of the brain that is called the “hunger center”. This center works like a break on the stomach and the intestine. As long as the blood has sufficient food, the hunger center slows down the action of the stomach and the intestine. When food is missing from the blood, the hunger center makes the stomach and intestine more active. That is why a hungry person often hears his stomach rumbling.
Intense muscle contraction, called hunger contraction, occurs when the stomach has been empty for several hours. These are increased by a low level of glucose in the blood. When we are hungry, our body doesn’t want any special food-it just wants nourishments. A very calm person can live longer than an excitable one because the protein stored up in his body is used up more slowly.