May 12, 2023 – A latest study of how the brains of lean and obese people reply to nutrients may explain why it's difficult for people to drop some pounds and keep it off.
Researchers at Yale University injected sugar (glucose), fats (lipids) or water (as a control group) directly into the stomachs of 28 individuals who were considered slim (defined by body mass index) and 30 individuals who were classified as obese after which observed their brain activity using magnetic resonance imaging.
Bypassing the mouth put the concentrate on the gut-brain connection and showed how people responded without tasting or smelling the food, said Mireille Serlie, MD, lead writer and professor of endocrinology at Yale School of Medicine CNN.
Imaging showed that in individuals who were lean or of normal weight, brain activity slowed and levels of dopamine, a chemical that triggers the sensation of “reward” from eating, increased. In people considered obese, nevertheless, brain activity didn't slow and dopamine was not released, in response to the study, published in . Natural metabolism.
Participants classified as obese were then enrolled in a 12-week weight reduction program. Individuals who lost at the very least 10% of their body fat underwent gastric infusion and brain imaging again, but weight reduction didn't change their brain's response.
“Nothing has changed – the brain still hasn't perceived satiety or satisfaction,” Serlie told CNN. “Now you might say three months isn't long enough or they haven't lost enough weight.”
“But this finding could also explain why people successfully lose weight and then regain all the weight a few years later – the effects on the brain may not be as reversible as we would like.”