Two mechanisms prompt us to seek food. Hunger is a physiologic drive for food that occurs when the body senses that we need to eat. The drive is nonspecific because when you’re hungry, a variety of foods can satisfy you. After recently finishing a nourishing meal, hunger probably won’t compel you to go eat a piece of that chocolate cake or apple pie. On the other hand, appetite is a psychological desire to consume specific foods. When environmental cues such as the sight of cake or the smell of coffee stimulates our senses, it prompts us to pleasured emotions and memories. People commonly experience appetite in the absence of hunger which is why we may crave cake and coffee after eating a full meal.
It is also possible to have a psychologic need for food yet have no appetite, also known as anorexia. This can accompany a variety of illnesses from infectious diseases to mood disorders. It can also occur due to a side effect on some medications such as chemotherapy used in treating cancer patients.
The primary organ that produces the sensation of hunger is the brain. The region of brain tissue responsible for telling us that we’re hungry is the hypothalamus. The hypothalamus triggers feelings of hunger or fullness by creating signals from nerve cells in other body regions and from hormones which are chemical messengers.
One hunger regulating signal comes from special cells lining the stomach and small intestine that detects changes in pressure to whether the organ is empty or has food. The cells communicate this data to the hypothalamus. Hormones are chemical messengers that are secreted into the bloodstream by one of the endocrine glands of the body. Their presence in the blood helps regulate one or more body functions. Insulin and glucagon are 2 hormones that are produced in the pancreas that are responsible for maintaining blood glucose levels. Glucose is the bodies most readily available fuel supply. When we have no eaten in a while and our blood glucose levels drop, the hormones tell the hypothalamus that we need more glucose in our bodies. After we eat, the hypothalamus picks up the sensation of a full stomach and a rise in blood glucose levels. However, even though the brain sends a clear signal to us that we are full, most of us ignore these signals and eat when we aren’t truly hungry. There are also other hormones responsible for stimulating food intake but I will not go into detail about them.
Foods that have protein in them have the highest satiety value. For example, a ham and egg breakfast will keep us full for a longer period of time than pancakes with syrup even if they both contain the same amount of calories. Also, high fat diets have a higher satiety value than high carbohydrate diets. Another factor that comes into play is how much fiber and water is within the meal consumed. Bulky meals tend to stretch the stomach and small intestine sending signals back to the hypothalamus telling us we’re full. Beverages tend to be less satisfying then solid foods which is why it’s important to limit high sugary beverages in our diets because it will most likely cause us to over eat and not feel full.
The factors that influence our appetite have to do with our sensory data, social and cultural cues and learning. Foods stimulate our five senses. Foods that are prepared and arranged with several different colors and shapes appeal our sense of sight. Food producers know this and spend millions of dollars annually in the US to promote and package their products this way. The aromas of foods are also powerful stimulants. The sense of sell is so acute that newborn babies can distinguish the scent of their own mother’s breast milk from other mothers. Much of our ability to taste foods actually comes from our sense of smell which is why foods aren’t as appealing when we have a stuffy nose. Texture is also important because it stimulates nerve endings sensitive to touch in our mouths and tongues. Our sense of hearing can also be stimulated by foods. For example, the fizz of cola or the crunch of peanuts or the “snap, crackle, pop” of Rice Krispies cereal can all have an influence on what we consume.
The brain associates certain social events such as birthday parties or holiday gatherings to stimulate our appetite. Especially at these times, our culture gives us permission to eat more than usual. Even when we feel full, these cues can motivate us to accept more than one serving. Some may also be triggered to eat more during certain activities such as watching TV or studying or at certain times of the day. Also in some cases, appetite may be a response of an emotional event that has happened. For example, after receiving a bad grade or arguing with someone may reach for more food when they’re not hungry. Many people crave food when they’re worried, frustrated, bored or are at a party. Some also seek food as a reward when good things happen to them.
All of these factors come into play when we desire certain foods. So the next time you’re feeling emotional or are at a gathering with lots of food, think before you eat. Do you really need those extra calories or fat in your body? Although it will taste delicious at that moment, how will you feel afterwards? Keep in mind of how much exercise it will take to burn off all the extra calories consumed when these events take place. Stick to whole, fresh foods and your cravings will eventually disappear!