The feeling of satiety would be triggered by a change in shape of brain cells after a meal

Globally, two billion people are overweight (BMI between 25 and 30) or obese (BMI equal to or greater than 30). In France, 17% of the adult population is obese, according to the latest estimates. The causes behind this disease are multi-factorial. Genetics, hormonal disturbances, endocrine disruptors, psychological and social weaknesses, physical inactivity, pollution or even low income can be taken into account. In obese subjects, the neural circuits that govern feelings of hunger and satiety in the brain, thus maintaining a balance between energy intake and expenditure, could also be deregulated, according to some researchers. Today, at the time of World Obesity Day, French scientists have understood the mechanisms behind the feeling of satiety: it would be a cascade of reactions triggered by the rise in the level of glucose in the blood. The results of their study, conducted in mice, appeared in the journal Cell Reports.

Here, researchers from CNRS, Inrae, the University of Burgundy, the University of Paris, Inserm and the University of Luxembourg were interested in the POMC neurons of the hypothalamus, basically of the brain, known to limit food. They receive a large number of nerve endings from other regions of the brain and their connections are very flexible. These can be done and undone very quickly depending on hormonal fluctuations. Working on mice, the researchers observed that after a balanced meal, the animals’ hormonal circuit was not changed.

In contrast, other nerve cells associated with POMC neurons, called astrocytes, change shape. Normally, they closely cover the POMC neurons and “act a little like brake pads, limiting their activity ”, explains the CNRS in a press release. However, after a meal, the blood glucose level, blood sugar, rises temporarily. This signal is then felt by astrocytes which retract in less than an hour. With the brake released, the POMC neurons activate. This triggers the feeling of satiety.

The mysteries of lipids and sweeteners

However, a meal high in fat does not cause this change. Today, scientists therefore want to determine whether lipids would not trigger satiety by another circuit. It also remains to be seen whether sweeteners have the same effects or are “real lures for the brain that only provide the addictive sweet sensation without suppressing hunger ”, indicates the CNRS.

If in people suffering from obesity, the plasticity of these neural circuits could be impaired, many people do not receive a signal of satiety in their body, which leads them to exceed a threshold reached for a long time and to finish meals on heart at the edge of the lips.

To avoid this, just change your habits. First, try not to eat anything for four hours to get really hungry. If you never experience this feeling, you may always eat “early” to fill a fear of missing out. If you are hungry all the time, you confuse d’elsewhere perhaps physiological hunger and psychological hunger.

Eat slowly and calmly to recognize satiety

So wait until you feel gurgling in the stomach to eat something (it is recommended to eat meals at the same time each day). Once food is close at hand, do not throw yourself on it. Chewing about twelve times before swallowing also sends signals to the brain’s reward. If you gobble up your food, your brain will not receive the information and it will take longer to feel full.

Eating peacefully is also recommended. Avoid eating while standing, walking, watching TV or answering an email as this distorts your relationship to food. Indeed, if you do something else at the same time, you forget that you are eating, it becomes automatic. Hence the principle of mindfulness, which scientists and nutritionists are talking about more and more. Inspired by Buddhism, the practice of mindfulness meditation began to develop in the medical community in the 1970s in order to manage the stress and chronic pain of the sick. Today it is used more and more in the area of ​​personal development.

In France, many such programs are now offered for people wishing to lose weight. However, they are far from accessible to all. For example, “Mindful Eating” offers to help you improve your relationship with food, without going through a private diet, for the sum of 480 €.

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