What we consume is influenced not only by physiological internal stimuli such as hunger, satiation and thirst, but also by psychological and social external stimuli such as fixed meal times or predetermined packaging and portion sizes.
Hunger and saturation – biological control of food intake
Physiologically, the beginning or the end of a meal and thus the energy intake is controlled by the perception of hunger and satiety. Hunger and satiety can be triggered by signals from inside or outside. Internal signals are, for example, the filling state of the stomach, the nutrients in the blood or hormones such as leptin, insulin or ghrelin. External signals can be, for example, a look at the clock (“At 7 o’clock I always eat!”) or an XL menu on special offer. Hunger suppressing, on the other hand, could be a disgusting sight or a repulsive smell.
The control center for hunger and saturation is in the hypothalamus. Here signals from the periphery (e.g. from the gastrointestinal tract) are modulated and converted into corresponding behaviours. Previously, the hypothalamus was thought to play the sole role in the regulation of food intake. Today it is known that the hypothalamus is integrated into a “neuronal network” and receives signals from other brain areas – e.g. from the limbic system. This explains why our food intake is also influenced by emotions and external stimuli.
Our eating habits are subject to many influences
Learning processes take place at every meal, which can lead to a preference or rejection of food. External factors such as environment, memories and moods influence the learning process (experience atmosphere). We strive for enjoyment and palatability (“maximizing enjoyment”). Already in the early mother-child interaction, emotional experiences with food intake influence later nutritional behaviour.
Some preferences (sweet, salty, greasy) and aversions (bitter, sour) are congenital to us and also protect newborns. There are hardly any sweet-tasting poisonous plants. These are usually bitter. This is why we humans do not like bitter from an evolutionary point of view, as it could warn us of possible poison. The younger a person, the less he normally likes bitter food.
Primarily the choice of food is controlled by learned preferences and aversions, whereby the taste naturally plays a strong role.
Biology of the sense of taste
In the mouth and throat area there are taste buds, whereby humans can perceive the 5 taste qualities sweet, salty, bitter, sour and umami. Researchers may have recently discovered other senses for fat and starchy foods. The palatability or texture of a food influences the amount and speed of food intake (“fatty versus lean”) and thus affects the feeling of satiety. In addition, one can already be full of a food (specific sensory saturation), but something else is still gladly eaten – e.g. a sweet dessert after the salty main course.
Characteristics of taste preferences
Newborns have from birth a natural preference for the taste sweet and an aversion to the tastes salty, sour and bitter. The differentiation of the later individual taste preferences usually takes place between the ages of 6 and 12 and is strongly determined by contact and experience with certain foods. When children are served a dish, they begin to like it after repeated contact (“liking by tasting”). Similarly, the observation of others eating food leads to the fact that these foods are perceived as attractive after some time (“mere exposure effect”). Thus, taste preferences and aversions also arise under social guidance and observation of others.
Motives in food selection change
At an advanced age, attitudes and experiences in food selection become increasingly important and gradually replace internal physiological stimuli. In the beginning it is important to satisfy hunger. With increasing age, external stimuli and attitudes increasingly influence the choice of food. Nutritional behaviour also always takes place in a socio-cultural context and is subject to trends.
The development and development of our nutritional behaviour is a complex process that is subject to neurobiological and social influences.