The Hunger Motive
When you're hungry, you eat. It seems like a simple and straightforward process, but the reality is that the hunger motive is influenced by biological, psychological, cultural, and social factors. One element alone doesn't make you hungry; rather several occurrences working together to provide the body with energy trigger the motive to eat. Homeostasis contributes by regulating metabolism and digestion via monitoring supplies needed to produce nutrients, while satiety sensors (as first encountered in relation to the thirst motive) serve as lookout stations set up to detect when supplies are on the way. On a more abstract level, external influence and culture-specific rituals can sometimes stimulate your desire to eat by recalling memories of how certain foods or celebrations made you feel euphoric.
Homeostasis Gets the Ball Rolling
One of the main reasons you experience hunger is that your body tells you it is so. Much like a new mother learns to distinguish between her baby's cries for hunger, cries for discomfort, and cries for sickness, a person who is “in tune” with his body learns to differentiate between hunger pangs and nervous rumblings. If you listen to your body, the hunger subsides; however, if you ignore the signals your body gives off, more signals will be given — physical weakness and lethargy, for example.
While all this action takes place externally, a different kind of internal action is responsible for what eventually produces the hunger pangs you experience. In order for your cells to function properly, nutrients must be made available. This is the primary goal of digestion. Food goes in, breaks down into simpler compounds, and gets recycled into concentrated forms of energy. Glucose, or the primary sugar found in blood, is a major source of energy for the brain and can be regulated either by obtaining it from the liver's storage supply or by eating food.
Sensors Make Sense
Now that you know you're hungry, how do you know when you're full? In other words, how is the body informed that nutrients will eventually be present if digestion itself takes four hours to complete? The decreased desire to eat is known as satiation, and the body sends off a number of satiation signals to let you know when to stop eating. Sensors located in the stomach and liver let the body know that nutrients will be coming shortly. Stretch receptors in the stomach send sensory information to the brain stem, alerting your body that the stomach is full. Psychological factors play an important role as well. After polishing off a big plate of spaghetti, eating more spaghetti seems very unappealing.
The desire to eat food that you know tastes good is often mistaken for the need to eat it. After consuming a satisfying, seven-course meal that made you feel “stuffed,” why would you continue to eat when dessert is brought to the table? You already fulfilled your body's request for food, so it certainly has nothing to do with your need for it.
An abstract idea concerning eating habits involves “the holidays,” a three-month period in which massive quantities of food are readily available at almost any given time at any given place. Why do we continue to prepare and eat so much food year after year during the holidays when we know it is not necessary to our physical well-being? Because these rituals are part of the customs that define our culture and society, and since we are members of that society, our participation in the rituals is an expression of celebration.
Memory can provide a possible explanation. Remembering how you felt the last time you ate dessert might trigger your desire to feel that way again if the reaction was favorable. And, considering the amount of sugar most desserts are made with; the “rush” one feels after eating dessert is similar to the feeling of euphoria.