Appetite and sense of satiety
Appetite is a desire that we all know very well. Understanding how appetite develops can help to successfully manage your personal ideal weight. Appetite is a key signal that determines what we eat and how much of what we eat. Basically it is an intuitive process: we eat when we are hungry and stop when we are full. But appetite is not a condition for eating. Our eating habits are also linked to habit. In addition, we humans can also feel pleasure while eating.
But how does our brain know when and how much we should eat?
To do this, our brain processes signals from our body, always with the aim of keeping our energy stores as full as possible. Signals of fullness and satiety are monitored both during and after eating. In addition, our brain also checks our fat stores and adapts our appetite if necessary, as the fat stores should be maintained as much as possible. This is particularly relevant with regard to changes in our appetite over a longer period of time.
When we eat food, our stomach expands and a signal about the volume of our food is sent to the brain. After the food leaves our stomach and passes into the small intestine, the amount of fat, carbohydrates and protein is determined and also transmitted to the brain. Both signals are processed in the brain stem, which is responsible for the feeling of satiety. All signals from the stomach and small intestine are collected there until a threshold is reached and satiation occurs.
How do we achieve a feeling of satiety?
Here it is particularly interesting to note that the amount of calories we consume through food and the resulting feeling of satiety are only loosely related. A study has taken a closer look at this and identified factors that determine food satiety:
- Calorie density: number of calories (kcal) per unit volume
Foods with low calorie density make us feel fuller per calorie consumed. Fibre and water are responsible for this. For example, if you eat 100 kcal crackers, you will feel less full in comparison to 100 kcal oatmeal, which contains a lot of water and fibre. Water and fibre are responsible for the fact that more space is needed in the stomach, which expands more and sends a higher signal of satiety to our brain, but without eating more calories. - Proteins and fibre: make us feel fuller per calorie consumed
- Palatability: the better a food tastes, the less full it makes us. The brain reduces the feeling of satiety when we eat something particularly good, because it wants to give us more of it.
Because of all these properties, we need to eat more calories from certain foods to develop a feeling of fullness. Since most of us eat until we feel full, especially foods with a high calorie density cause us to eat more than necessary without realizing it. Here is an overview of foods that have a high and a low calorie density and therefore saturate us less or more.
High calorie density - not very filling: white bread, croissants, donuts, crisps, ...
Low calorie density - very filling: potatoes, meat, fish, oatmeal, fruit, ...
References:
Get SH, Miller JC, Petocz P, Farmakalidis E. A satiety index of common foods. Eur J Clin Nutr. 1995;49(9):675-690.