The major cause for feeling hungry lies in the blood circulation. Levels of different substances are generally maintained in the blood mainly by the digestive system./ One of the major substance is glucose. When its level in the blood falls, we get the hunger pangs in the stomach. This involves the production of the hormone such as ghrelin. Ghrelin is secreted by the walls of the stomach.Hunger contractions start to occur in the stomach due to hunger generating signals that reach the brain.Hunger pangs continue to upto 30-45 mins.