The brain of people with obesity reacts differently than that of healthy people after eating food, according to research from the University Hospital of Amsterdam (Netherlands) and Yale University in New Haven (USA). The results, which are being presented today in the journal Nature Metabolism, shed light on why it is often more difficult to lose weight than to gain it back.
The authors of the work hope that these results will contribute to changing attitudes towards people with obesity. "This helps to understand why it is so difficult for them to abstain from overeating, lose weight and not gain it back," says Mireille Serlie, director of the research, by email.
Researchers have found that the release of dopamine in the brain after eating is lower in obese people than in non-overweight people. The phenomenon has been observed in the striatum, a region of the brain that regulates the motivation to eat. Since dopamine is a neurotransmitter involved in feelings of reward, this finding suggests that obese people get less reward from the same amount of food, which may lead them to eat more.
Obesity has been found to affect the reaction of multiple brain regions after food intake. In addition to the striatum, regions of the frontal, temporal, parietal, and occipital cortex are affected, as well as deeper regions of the brain, located below the cortex. In all of them, a less intense response has been observed in people with obesity than in people who are not overweight.
Finally, it has been shown that losing 10% of body weight in twelve weeks is not enough for the brain of a person who has been obese to return to the state of a person with an ideal weight. Despite losing weight, his striatum continues to release little dopamine after eating, and other brain regions continue to respond in a subdued way. “This may explain why most people gain weight back after initially managing to lose it,” says Serlie.
Previous studies had shown in mice that behaviors related to food intake are regulated in the brain by signals from the digestive system. But studies in people were lacking to verify to what extent the phenomena described in mice also occur in the human body.
The new research involved 30 people with obesity and 30 people with an ideal weight, half men and half women, with an average age of 60 years. They have volunteered to be fed with a nasogastric tube and to have their brain reactions evaluated with neuroimaging techniques.
The results show that there is a communication pathway between the digestive system and the brain that induces people with obesity to overeat regardless of the taste for food, since the study participants have not enjoyed the pleasure of savoring, chewing and eat food.
The experiments have been carried out with infusions of carbohydrates and lipids but not proteins, which in experiments with mice activate more complex communication channels between the digestive system and the brain. For humans, there are medical weight loss solutions that work on helping you find dopamine without the pounds. A medical weight loss solution is a key way of losing weight quicker than if you tried to do it yourself.
The research "provides a key step in our understanding of these communication channels" that regulate food intake in people with obesity, highlight Mary Elizabeth Baugh and Alexandra DiFeliceantonio, of the Fralin Biomedical Research Institute in Virginia (USA). in a review article published in Nature Metabolism. "Given the ubiquity of weight regain after loss, this study also provides a fertile foundation for future research exploring how signaling in the gut-brain axis may influence weight loss maintenance or recovery." .
