Choosing what to eat is never as simple as just picking a doughnut, a plate of fruit or a steak. Scientists attribute food choices to biology, which determines how the body reacts to certain foods, and to signals sent throughout the body.
Contrary to the simplistic notion that we eat calories when we are hungry, scientists say that visual, auditory, olfactory and gustatory cues influence our food choices.
An article by Alex Johnson, Associate Professor of Behavioural Neuroscience at Michigan State University, shows that visual cues, such as the packaging of fast food or the glow of a light when food is served, can shape our taste preferences. He explains that these cues can even override our bodies' energy needs, leading to overeating behaviour.
He explains that our ability to learn about food-related cues goes beyond external stimuli. Internally, our bodies provide cues, such as feelings of hunger and fullness that come from the gastrointestinal tract. This then influences decisions about when to eat.
Prof Johnson also explains that there is a biochemical link between the gut and the brain that shapes eating behaviour. The link, through the vagus nerve, which controls specific body functions including digestion, communicates nutrient information to the brain, inducing a state of pleasure that influences food preferences and choices.
Poor awareness has also been linked to dysfunctional eating behaviours such as eating disorders. For example, anorexia (an eating disorder characterised by abnormally low body weight and intense fear of gaining weight) can occur when hunger does not motivate eating, while a lack of satiety signals can contribute to binge eating.
Especially during the holiday season, external stressors such as social obligations, societal pressure and guilt can affect eating habits.
A study titled Eating With Our Eyes: From Visual Hunger to Digital Satiation, states that “the sense of vision provides an effective means of foraging, predicting which foods are likely going to be safe and nutritious to consume, and generating those expectations that will constrain the consumption experience.”
The study explains that the brain supports our search for nutritious foods by relying on vision, allowing us to choose energy-rich foods and/or fruits based on colour.
“The human brain evolved during a period when food was much scarcer than it is now and it would appear that our genetic make-up still seemingly drives us toward consumption whenever food is readily accessible. ‘Visual hunger’ – a natural desire or urge to look at food – could well be an evolutionary adaption: Our brains learnt to enjoy seeing food, since it would likely precede consumption,” the study says.
“The automatic reward associated with the sight of food likely meant another day of sufficient nutrients for survival, and at the same time, the physiological responses would prepare our bodies to receive that food. Our suggestion here is that the regular exposure to virtual foods nowadays, and the array of neural, physiological, and behavioural responses linked to it, might be exacerbating our physiological hunger way too often,” it adds.
According to the study, research conducted in laboratories has demonstrated that watching food-related television programs can influence people's energy intake patterns from a given selection of available foods.
"This exposure also leads to an elevated consumption of calories in the meals individuals prepare for themselves, despite a decreasing amount of time spent directly engaging with food. This trend is evident as the consumption of processed, convenience foods, and ready-made meals continues to rise,” the study states.
“Nevertheless, it is important to note that the visual presentation, or plating, of food has a substantial impact on people's perception of flavour and can influence subsequent food choices and consumption behaviour.”
Another study published in Science Advances established that early experience with food influences taste preference in adulthood. This connection relies on how our early encounters with food affect the brain. The biology is consistent across mammals.
While conducting the study, researchers from the Department of Neurobiology and Behavior in the Renaissance School of Medicine and College of Arts and Sciences exposed groups of mice to different flavour solutions for one week.
These groups, either weanlings (exposed early) or adults (exposed later), were then returned to their regular, nutritionally balanced but less flavourful diet. In comparison, a control group of mice exclusively consumed only the standard, less palatable diet.
Several weeks after the one-week taste exposure, the researchers measured the preference for a sweet solution over water. Mice exposed to taste variety early in life showed an increased preference for sweet tastes in adulthood compared to the control group.
This shift in preference was dependent on a mix of taste, smell and gut-to-brain signals specifically linked to early taste exposure.
Mice exposed to a variety of tastes in adulthood did not show a distinct sweet preference compared to their age-matched control group. These findings underscore that taste experiences influence preferences, but only if they occur within a specific developmental window.
The research team also monitored the activity of neurons in a brain region involved in taste perception and food intake decisions in all the mice. The recorded activity showed that the change in sweet preference was associated with fluctuations in the activity of inhibitory neurons in adult mice.
In humans, the study authors explain that our tendency to prefer foods from our childhood may have been influenced by our culture and related taste experiences. In addition, from a public health perspective, several neurodevelopmental and neurodegenerative disorders often correlate with increased or decreased taste sensitivity.
This suggests links between taste perception and brain function in both health and disease.
They have also found that bacteria in the gut help a host animal to identify the missing nutrients in food and to adjust the amount of those nutrients that the host really needs to consume. They would also tell the host what kind of food to eat.
