Losing weight: how does the brain know when the stomach is full?
On average, it takes 20 to 30 minutes for saturation to set in. That is why it happens to many – especially people who eat quickly – that they continue to eat beyond their natural satiety.
If you know how the digestive tract is used to convey a feeling of satiety to the brain, you can avoid both – and lose weight more easily.
Expansion of the stomach wall and absorption of nutrients satisfy hunger
The first step towards satiety takes place in the stomach itself. When food begins to fill the stomach, the stomach wall expands. Receptors report this to the brain.
However, this is not yet sufficient, as can be seen in the example of drinking. Liquid stretches the stomach, but when it comes to water or another low-calorie drink, it has no or not enough nutrients and energy to satisfy hunger, let alone satiate it.
The supply of nutrients and energy through the food supplied also play a role. Together with the expansion of the stomach wall, they influence the acute feeling of hunger, but do not yet bring about satiety. Certain hormones take care of this.
The release of certain hormones leads to satiety
Both hunger and satiety are communicated to the brain via hormones. In the hypothalamus there is a so-called satiety center, which processes information that is sent to the brain via the bloodstream through various hormones, above all leptin.
Further saturation signals are sent out via the release of the hormones cholecystokinin, insulin and the rise in glucose levels.
With continued food intake, the level of ghrelin – a growth hormone also known as the hunger hormone – also falls. Studies have shown that the ghrelin level is higher in the evening than in the morning, which explains why some people feel no or less appetite in the morning.
Study: Suspected direct communication path to the brain
A recent study from 2018 found reason to believe that the digestive system and brain communicate with each other in other ways. The researchers found synapses in a rare type of intestinal cell.
Synapses are neural connections that are located between nerve cells and sensory, muscle or gland cells and are responsible for communication between the cells.
This discovery is to be interpreted as an indication of a direct line of communication between the intestine and the brain.
Further influences on the feeling of satiety
Research cannot rule out a genetic influence on satiety. When exactly the saturation occurs and how long it lasts depends on the individual.
The set point theory states that these individual differences are based on the respective individual ideal weight of the person. According to the theory, the individual feeling of hunger and satiety strive to maintain this ideal weight as much as possible.
The evolutionary tendency to eat also has an indirect influence on satiety. Many people have been brought up in this way and have developed the habit of eating their plate empty. The feeling of satiety is explicitly ignored.
Anyone who eats according to this principle over the long term will at some point have problems consciously perceiving their feeling of satiety. With patience and conscious eating, however, the connection to your own feeling of satiety can be restored.
Tips to lose weight without going hungry
If you want to lose weight without going hungry, or simply want to increase your well-being by not eating beyond your natural feeling of satiety, the following tips can be helpful.
One study showed that eating speed is of great importance for satiety. By eating slowly, you give your body time to perceive the various signals of satiety in good time. The longer you eat, the longer your satiety hormones are released.
People who are overweight often have a habit of eating quickly. You will then be full more quickly, but in a shorter time you will take in more calories and release fewer satiety hormones.
As a result, they eat more calories than they need and feel less full.
Also, by taking breaks from eating, you give your body the chance to determine how full you are. Especially if you actually eat rather quickly, breaks can regulate your eating pace.
Digestion begins in the mouth, they say. Those who chew their food sufficiently often not only benefit from the taste of the food, but also prevent digestive problems and promote a good satiety.
The increased flow of saliva is also passed on as a signal to the brain. In addition, frequent chewing of the food also slows down the speed of eating.
It is said that every bite should be chewed 40 to 50 times. But you are already well advised if you start chewing 20 times per bite and generally make sure to chew more than usual.
Stop when you are full
Contrary to what most should have learned, your plate does not always have to be completely empty. Stop eating when you are full.
That doesn’t mean you have to throw away the leftovers. Leftover items are often ideal as a side dish for the next meal, can be integrated into it in another way or can serve as a quick snack for in between the next day.
Qian, J. et al. (2018): Ghrelin is impacted by the endogenous circadian system and by circadian misalignment in humans, accessed on September 23, 2021: https://pubmed.ncbi.nlm.nih.gov/30232416/
Bohórquez, DV, et al. (2018): A gut-brain neural circuit for nutrient sensory transduction, accessed on September 23, 2021: https://pubmed.ncbi.nlm.nih.gov/30237325/
Harris, RB (1990): Role of set-point theory in regulation of body weight, accessed on September 23, 2021: https://faseb.onlinelibrary.wiley.com/doi/10.1096/fasebj.4.15.2253845
Angelopoulos, T. et al. (2014): The effect of slow spaced eating on hunger and satiety in overweight and obese patients with type 2 diabetes mellitus, called on September 23, 2021: https://pubmed.ncbi.nlm.nih.gov/25452861/