Do you eat with your eyes, intestines, or mind?

The festive season has arrived, and with it the opportunity to enjoy festive sweets. The adage "You eat with your eyes first" seems especially relevant at this time of year.

However, the science behind eating behavior reveals that the process of deciding what to eat, when and how much is far more complicated than just consuming calories when your body needs fuel. Hunger signals are only part of why people choose to eat. As a scientist interested in psychology and biology that drives eating behavior, I'm fascinated by how brain experiences shape eating decisions.

So how do people decide when to eat?

Eating with your eyes

Visual signals related to food can shape feeding behaviors in both humans and animals. For example, packaging food in McDonald's packaging is enough to boost taste preferences across a range of foods from chicken nuggets to carrots in young children. Visual cues related to food, such as providing light when delivering food, can also reinforce binge eating behaviors in animals by exceeding energy needs.

In fact, a whole host of sensory stimuli – noise, odors, and textures – can be associated with pleasant consequences of eating and influencing food-related decisions. That's why hearing an attractive radio tone for a food brand, watching a TV commercial for a restaurant, or walking next to your favorite restaurant can affect your decision to consume and sometimes overeat.

However, your ability to recognize food-related cues extends far beyond just stimuli from the outside world and includes the internal environment of your body. In other words, you also tend to eat with your stomach in mind, and you do so by using the same learning mechanisms and brain involved in processing food-related stimuli from the outside world. These internal signals include feelings of hunger and fullness emanating from the digestive system.

It's no surprise that signals from your gut help determine when to eat, but the role these signals play is deeper than you might expect.

Trust how you feel

Feelings of hunger or satiety act as important signals that influence food decision-making.

To study how objections to eating behaviors are formed, researchers trained lab mice to link feelings of hunger or satiety to whether they received food. They did this by giving mice food only when they were hungry or full, so that the mice had to recognize those internal signals to calculate whether food would be available or not. If mice are trained to expect food only when hungry, they will generally avoid the area where food is available when they feel full because they do not expect to be fed.

However, when the mice were injected with a hunger-inducing hormone called ghrelin, the mice approached the food delivery site frequently. This suggests that the mice used this artificial state of hunger as an interceptor signal to predict food delivery, and then behaved as if they expected food.

Interceptions are sufficient to shape feeding behaviors even in the absence of external sensory signals. One particularly striking example comes from mice that have been genetically modified so that they are not able to taste food but nevertheless show preferences for certain foods only through their caloric content. In other words, rodents can use internal cues to shape their food decisions, including when and where to eat and which foods they prefer.

These findings also suggest that feelings of hunger and nutrient detection are not limited to the stomach. They also include areas of the brain that are important for regulation and balance, such as the lateral hypothalamus, as well as brain centers involved in learning and memory, such as the hippocampus.

What's happening in the vagus

The gut-brain axis, or biochemical communication between your gut and brain, shapes nutrition behaviors in many ways. One of them includes the vagus nerve, the cranial nerve that helps control the digestive system, among other things.

The vagus nerve quickly transmits nutritional information to the brain. Activation of the vagus nerve can lead to a pleasant state, in which mice perform voluntary behavior, such as inserting their nose through an open port, to stimulate the vagus nerve. More importantly, mice also learn to prefer foods and places where vagus nerve stimulation occurs.

The vagus nerve plays an essential role not only in the delivery of digestive signals but also in a range of other interstitial signals that can affect how you feel and act. In people, vagus nerve stimulation can improve learning and memory and can be used to treat major depression.

Benefits of Interdisciplinary Awareness

Your body's ability to use both external and internal signals to regulate how you learn and make food decisions highlights the impressive processes involved in how you regulate your energy needs.

Poor inner awareness is associated with a range of dysfunctional feeding behaviors, such as eating disorders. For example, anorexia may occur when interstitial signals, such as feelings of hunger, are unable to stimulate motivation to eat. Instead, the inability to use the feeling of fullness to mitigate the rewarding and enjoyable consequences of eating delicious food can lead to binge eating.

Your interstitial signals play an important role in regulating daily eating patterns. During the holidays, many stressors from the outside world surround eating, such as crowded social calendars, pressures to comply, and guilt for overeating. At this time, it's especially important to establish a strong connection to your interstitial signals. This can help promote intuitive eating and a more holistic approach to your eating habits. Instead of focusing on external factors and placing conditions on your eating behavior, enjoy the moment, deliberately taste every bite, and make time for your interception signals to work in the role you were designed to play.

Your brain has evolved to feel your current energy needs. By combining these cues with your experience of your eating environment, you can improve your active needs and enjoy the season.

Alex Johnson, Associate Professor of Behavioral Neuroscience, Michigan State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.