2023-06-12 17:01:16
Many obese and overweight people follow successful diets and manage to lose the desired kilos. However, in a large part of them they regain their weight easily. Now a team of Dutch and US researchers may have been right.
In an article published in the magazine «Nature Metabolism», researchers have seen that brain responses to specific nutrients are decreased in people with obesity and do not improve after weight loss. This information could explain why most people regain weight after initially successful weight loss.
The findings suggest that long-lasting brain adaptations occur in people with obesity, which could affect eating behavior. “We found that people with obesity released less dopamine in an area of the brain important for the motivational aspect of food intake compared to people with a healthy body weight. Dopamine is involved in the rewarding feelings of eating food,” says Mireille Serlie, lead researcher and professor of endocrinology at the UMC of Amsterdam (The Netherlands).
Obese subjects also showed reduced responsiveness in brain activity following infusion of nutrients into the stomach. “Overall, these findings suggest that nutrient sensing in the stomach and intestine and/or nutritional cues are reduced in obesity and this could have profound consequences for food intake,” adds Serlie.
Food intake depends on the integration of complex metabolic and neural signals between the brain and various organs, including the gut and nutritional signals in the blood. This network triggers feelings of hunger and satietyregulates food intake as well as the motivation to search for food.
Although these processes are becoming better understood in animals, even in the context of metabolic diseases such as obesity, much less is known about what happens in humans. Partly due to the difficulty of designing experimental setups in the clinic that could shed light on these mechanisms.
To address this lack of knowledge, Serlie, who is also a professor at the Yale University (USA)both institutions designed a controlled trial.
Nutritional cues are reduced in obesity and this could have profound consequences for food intake
The trial involved infusing specific nutrients directly into the stomachs of 30 participants with a healthy body weight and 30 people with obesity, while simultaneously measuring their brain activity using MRI and dopamine release using SPECT scans.
While participants with a healthy body weight showed specific patterns of brain activity and dopamine release after nutrient infusion, these responses were severely attenuated in obese participants.
Furthermore, loss of 10% of body weight (following a 12-week diet) was not sufficient to restore these brain responses in people with obesity, suggesting that long-lasting brain adaptations occur in the context of obesity and that they remain. even after achieving weight loss.
“The fact that these responses in the brain are not restored after weight loss may explain why most people regain weight after initially successful weight loss,” Serlie concludes.
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