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NutrInsight • About the value of controlling appetite
Although cells use energy substrates continuously, eating behaviour consists of discontinuous episodes. In animals this is regulated by hunger/satiety, which modulates the amount of energy consumed during eating, but also the intervals between consecutive eating episodes. In human beings, the phenomenon is more complex, because, in addition to hunger/satiety, it also involves psychological and sociological factors: we have to feed our body to compensate for its energy expenditure, we have to respond to our senses to satisfy our hedonic needs, and nourish our «civilised» brain in order to satisfy our cultural needs. This search for food is dictated by an internal motivation: our appetite. This document is intended to clarify all the concepts related to appetite, hunger, satiety and satiation; to describe some of the behavioural and physiological markers used; and, finally, to provide an update about some of the factors that influence the regulation of appetite.
The human appetite results from complex interactions between the physiological, psychological and environmental factors that produce a profile of motivations and eating habits that reflect the regulation of appetite over time.
The individual’s daily food intake results from a succession of eating episodes over the course of the day, characterized by various factors including their frequency, their size, their content and when they are consumed. The internal regulation of food intake is based on two main mechanisms: satiation (which leads the person to stop eating) and satiety (which controls the interval between two successive intakes of food). These finely- tuned mechanisms are intended to maintain the energy balance (the equilibrium between energy intake and expenditure that makes it possible to maintain a stable bodyweight), on condition that the person does not ignore these physiological signals. The search for sensory pleasure, reducing stress, social pressure and boredom are all examples of other motivations to eat.
Are all food intakes equivalent? A wide range of terms is used to describe the eating sequence, and there is no consensus about which is best.
What constitutes a «meal» or «nibbling» or «snacking» has not been clearly defined, and the criteria used vary from one investigator to another (1). Taking the physiology of eating behaviour into account has made it possible to provide a new definition: a meal is an eating episode triggered by the sensation of hunger, induced by the lack of immediately available glucose. Nibbling is eating that is not motivated by the sensation of hunger (in other words, which occurs when the individual is in a state of satiety), but by boredom, stress, greed, etc. (2;3). Depending on the size of the meal, a distinction can be made between the traditional main meals (breakfast, lunch, dinner) to which can be added a teatime snack, or other light snack. As long as these different meals correspond to a physiological need and so do not lead to over-eating (a positive energy balance), increased eating frequency can have beneficial health effects (4).
1.1 Appetite, the trigger for eating
Main components of appetite
Appetite can be described as the internal motivation that leads the person to look for food, to select it and to eat it (5). The expression of the human appetite results from the interaction between biological regulation (including physiological and psychological factors), and adaptation to the environment (Fig 1).
Appetite is therefore characterised by various parameters including the following:
- motivations to eat or subjective sensations (in particular that of feeling hungry),
- energy and nutrient intake resulting from eating, which are themselves influenced by dietary preferences, - the timing and size of meals and snacks.

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