satiety Humans and many animals eat in discrete periods of time, that is, they eat meals. Before a meal begins the sensation of hunger rises, and this motivates food-seeking behaviour. Once eating starts, hunger declines, and people report that they start to feel full. The term ‘satiation’ describes the processes that bring a meal to an end. An interval of time will then elapse before eating begins again. ‘Satiety’ refers to the inhibition of eating following a meal, and it is measured both by the inter-meal interval and by the amount consumed when food is next offered.

Let us consider in more detail what happens during a meal. At the beginning, eating is rapid, with few pauses between bites. As the meal progresses, eating slows, there are more pauses between bites, and other behaviours such as fidgeting, grooming, or resting increase. A state of satiety is reached when the meal ends. This state is usually associated with a pleasant sensation of fullness or satisfaction. However, unpleasant sensations of nausea and bloating can be associated with satiety following excessive food intake. Of interest is that even when eating has stopped altogether, the introduction of a new food can restart eating. We call this satiety for one food but not for others ‘sensory-specific satiety’. This specificity of satiety explains why, in a multi-course meal, dessert is eaten even when we feel full.

Satiation and satiety depend both on behavioural and physiological responses. The act of eating and our beliefs about what we are eating are important. As food is ingested, a number of physiological processes are sequentially activated. We chew food and it then moves down our throats and into our stomachs, thereby stimulating receptors which respond to the bulk of food and the nutrients it contains. Distension of the stomach and gut makes us feel full. The gut also releases hormones which affect satiety. All of these responses to food occur within minutes of eating, but the metabolism of food, that is turning it into fuel several hours later, also affects satiety or when we will eat again.

Much recent research has explored how different types of foods affect the satisfaction and feelings of fullness that follow eating. While the calorie content of food can influence satiety, another important factor is the weight or volume of food consumed. Since fat has more than twice the calories per gram as either carbohydrate or protein, a high-fat meal is smaller in size than a low-fat meal with the same number of calories. Imagine that before a meal you eat a first course of either tomato soup or an equivalent number of calories from cheese on crackers. The soup provides a greater bulk of food because it has a higher water content and little fat. You will feel fuller and hunger will be suppressed more following the soup than the cheese on crackers, thus you will eat less food during the main course. Understanding how different foods and nutrients affect satiety is leading to strategies to reduce energy intake and to control body weight. Eating a diet of low-fat, high-fibre, high volume foods such as fruits and vegetables is a healthy, natural way to increase satiety after a meal.

Barbara Rolls

Bibliography

Rolls, B. J. (1986). Sensory-specific satiety. Nutrition Reviews, 44, 93–101.

Satiety

Satiety is a feeling of fullness and satisfaction after eating. It is the opposite of hunger or appetite. The mechanisms and events that lead to a state of satiety are numerous, complex, and not well understood. It is believed that the release of certain hormones and the firing of certain nerves when food enters the intestine sends messages to the brain to signal that it is time to stop eating. Genetic predisposition and learned behaviors may affect at what point satiety occurs in an individual. Learning to stop eating when satiety is reached is an important component of weight control.

see also Appetite; Cravings; Weight Management.

Beth Fontenot

satiety The sensation of fullness after a meal.