Many people want to reduce their weight, but find the process challenging. Despite intentions to eat less or to eat foods lower in calories, people often find themselves eating more than they planned. Feeling hungry when cutting back can make losing weight a struggle. A look at the complex biology involved in appetite regulation can help us begin to understand why losing weight is not just a matter of willpower.
Our bodies basically tell us when to eat and when not to eat via biological messages in the form of hormones and neural signals that are constantly being sent between the brain and the rest of the body. This complex biological system is responsible for regulating our appetites and determining our body size. Understanding this system is important for clinicians, scientists, and drug companies who are trying to find ways to help people balance obtaining optimal nutrition with maintaining a healthy body weight. A glimpse of the complexity behind this system also can help the individual struggling with appetite control.
The names of the parts of the brain and the molecules that regulate hunger are often represented by several letters, which makes for a list that sounds like an alphabet soup (e.g. MC3, GLP-1, CART, and POMC). A visual diagram of all the components shows it to be very complex and interactive.
Biological Messages That Promote Hunger vs. Messages That Reduce Hunger
How the body regulates hunger can be looked at in terms of messages that promote hunger and messages that reduce hunger or produce a feeling of fullness. Interestingly, only a few of the many biological messages involved promote hunger. One of the molecules that promotes hunger is ghrelin, which is produced in the stomach and small intestine. In the brain, it stimulates the release of a hunger promoting chemicals from the hypothalamus, neuropeptide Y (NPY) & Agouti-related protein (AgRP). However, another hormone (leptin), which decreases hunger, actually contributes more to the message of hunger than ghrelin by promoting hunger and releasing these brain hormones when it is low. Leptin is produced by the body fat. Insulin, which is produced in the pancreas, also increases hunger in the body by causing uptake of glucose from the blood into the cells.
In contrast to the relatively simpler system that increases hunger, the majority of this complex appetite control system is engaged in reducing hunger. The list of hormones and neural signals involved in telling you when you have eaten enough and should stop seeking more food is a complex, long list, with many different molecules. One challenge for drug companies trying to develop weight loss medications is to determine which of these messages to attempt to modify in an attempt to support weight management.
How the Brain and the Rest of the Body Regulate Hunger
The system that regulates hunger also can be looked at in terms of biological messages that arise in the brain and those that arise in the rest of the body. Biological messages, in the form of neuropeptides or hormones, are initiated in both the brain and the rest of the body and involve interactions between the two areas. A message originating in one organ can impact another organ or the brain. We can look at the appetite regulation system in terms of having a “brain side” and a “body side”, but in reality they affect each other continually to up-regulate or down-regulate feeding behavior as needed.
The brain both promotes and reduces hunger. For example, it makes certain neuropeptides that increase the release of ghrelin in the body, increasing hunger, and also makes neuropeptides that decrease appetite or decrease the release of ghrelin.
On the body side, several other organs help regulate appetite, in addition to the stomach and part of the small intestine generating ghrelin. Other organs that produce hormones that affect hunger or satiety are the pancreas, liver, and body fat, which send out various hormones, both appetite-increasing and appetite-decreasing.
Some appetite regulating molecules act only in the brain or only in the body. Other hormones act both in the body and the brain, making their way from the body where they are produced through a partially resistant blood-brain barrier. For example, the hunger-promoting hormone ghrelin has effects both centrally in the brain and peripherally in the body, promoting hunger in both locations. Interestingly, some molecules have a different effect in different areas of the body. For example, although insulin increases hunger peripherally (in the body), it decreases hunger centrally (in the brain).
The Bigger Picture of Appetite Regulation
Other body systems participate in appetite regulation as well. It is not entirely an automatic biological process. Other influences on the appetite include mood, stress, associations, the brain’s reward system, and social pressures.
Are those of us who are trying to manage our weight at the mercy of all these appetite-promoting processes with messages coming from our bodies, brains, and the environment? The good news is that we can make intentional selections to reduce excess hunger by making healthy food and beverage choices that affect the biological messages described. A number of foods and eating patterns have been identified that help regulate the appetite, limiting food intake for better weight management. These include eating enough bulk, i.e., high fiber foods, drinking enough water, and eating meals high in protein. Eating patterns that promote better appetite regulation include avoiding high carbohydrate meals or snacks, avoiding added sugar, and avoiding unhealthy fats, such as trans fats added to make foods seem creamy. These choices act to promote satiety and decrease excessive hunger by helping to better regulate the complex biological systems involved in appetite control.
Health Impact Studios has multiple games currently in development that deal with hunger and healthy eating including GroceryHunt and Swipe Away. Learn more about our games in development.