- The intestinal microbiota, where a whole set of microorganisms live (bacteria, viruses, parasites and non-pathogenic fungi), influences a large part of the body, such as the immune system, the brain, the cardiovascular system or even the bone system.
- The hypothalamus controls the feeling of hunger but also thirst, stress and body temperature.
In France, 17% of the population, or more than 8 million adults, are obese, according to the Ministry of Solidarity and Health. Obesity is a major risk factor for several pathologies, such as heart and cardiovascular disease and type 2 diabetes.
Very often, the reasons for weight gain are too rich a diet and a lack of physical activity. However, a study published in the journal Science, April 15, highlights another factor: the absence of the Nod2 receptor in the brains of some people, which could explain why they are always hungry. But why ?
A predisposition to obesity due to our brain
According to scientists, the answer comes from the dialogue between our brain and our intestinal microbiota. Throughout the day, the brain and gut microbiota exchange a lot of information, including the need to eat. In detail, it is the hypothalamus that sends this signal. But scientists have observed that the absence or dysfunction of the Nod2 receptor, present both in immune cells and in neurons of the hypothalamus, promotes weight gain because the hypothalamus is then no longer able to transmit the right information to the microbiota. Thus, the person who no longer has the Nod2 receptor or if it is dysfunctional is still hungry even if they have eaten enough.
A global public health issue
To achieve this result, the researchers conducted their experiments on mice. They found that rodents that lacked the Nod2 receptor ate more than others and therefore tended to get fat. So far, no clinical trials have been conducted on humans, but scientists believe the results could be similar.
According to the authors, their discovery could therefore explain that some patients are more at risk of suffering from bulimia, diabetes or obesity. A major public health issue because, according to the World Health Organization, 1.9 billion adults worldwide were overweight in 2016 and 650 million were classified as obese.