A study discovers the mechanism by which excess fat in the diet can block communication between the brain and the digestive system, which would favor obesity and other health problems.

Ultra-processed and fast food are often characterized by excess added fats and sugars. This type of food is very caloric and is related to overweight, obesity, diabetes, cardiovascular diseases, intestinal dysbiosis (alteration of the microbiota and inflammation that leads to other diseases.

A study has discovered that excess fat contributes to this series of problems not only because of its inflammatory effect and calorie intake. Research reveals that, from a certain amount, fats alter the brain’s ability to regulate appetite. The work is a warning for people who continue to eat poor quality products and also for followers of high-fat diets, such as ketogenic, even if they do so with the intention of promoting health.

Researchers claim that a high-fat diet rewires the brain and reduces our ability to regulate appetite and calorie consumption. They have been able to verify that excess fat blocks communication between the brain and the digestive system. Specifically, astrocytes or stellate neurons, which participate in this communication, are affected.

FATS ACT ON NEURONS THAT CONTROL APPETITE

“Calorie intake appears to be regulated in the short term by astrocytes. We found that a brief exposure (three to five days) to a high-fat, high-calorie diet has a major impact on astrocytes, triggering the normal signaling pathway to control the stomach.

Over time, astrocytes appear to become desensitized to high-fat foods. After 10 to 14 days of following a high-fat, high-calorie diet, astrocytes seem unresponsive and the brain’s ability to regulate calorie intake appears to be lost. This disrupts signaling to the stomach and delays the way it empties,” says lead author Dr. Kirsten Browning, of Pennsylvania State University School of Medicine (Penn State), in a news release. The findings are published in The Journal of Physiology.

WHAT HAPPENS IN THE BRAIN WHEN YOU CONSUME A LOT OF FAT?

Astrocytes initially react to “junk food” by releasing chemicals called gliotransmitters, which stimulate the stomach’s neurons responsible for contracting and relaxing it to fill and empty in response to food passing through the digestive system.

When something inhibits astrocytes, communication between the brain and the digestive system is disrupted. The decrease in signaling chemicals leads to a delay in digestion, because the stomach does not fill and empty properly.

The researchers observed food intake control behavior in more than 200 lab rodents fed a normal or high-fat diet for one, three, five or 14 days. The authors combined observation with specialized genetic and pharmacological techniques to target different neural circuits. This allowed the team to specifically inhibit astrocytes in a particular region of the brainstem, the back that connects to the spinal cord.

“We still need to figure out if the loss of astrocyte activity and signaling mechanism is the cause of overeating or if it occurs in response to overeating. We are anxious to know if it is possible to reactivate the brain’s apparent lost ability to regulate calorie intake. If this is the case, it could lead to interventions to help restore calorie regulation in humans.”

WHAT ARE THE RECOMMENDATIONS ON FAT CONSUMPTION?

The Pennsylvania State University study offers no recommendations, but the World Health Organization advises that fats contribute no more than 30% of the calories consumed throughout the day. On the other hand, you have to select well the sources of fats among the healthiest foods. Extra virgin olive oil, whole nuts without salting or roasting (especially almonds, walnuts, hazelnuts, cashews and pistachios) and whole or crushed seeds (especially flax and sesame) are recommended.

On the other hand, refined oils, unidentified vegetable fats, palm oil, hydrogenated or partially hydrogenated fats and ultra-processed products (ready meals, ice cream, industrial pastries, pastries, etc.) should be avoided.