Yale Research Finds Obese Bodies Are Less Effective at Nutrient Sensing

A study conducted by Yale researchers may have found one of the underlying mechanisms that makes it so difficult for obese people to lose weight. Data from the paper published in Nature showed that, after feeding, obese people did not have the same brain response to nutrients as lean people and that brain activity did not change for obese participants even after losing significant weight.

In a single-blind, crossover study, researchers looked at the effect of glucose, lipids, and water on cerebral activity and striatal dopamine release among 30 people with healthy weight and 30 obese participants. Results showed that lean people experienced preference-independent and orosensory-independent nutrient-specific neuronal responses, while obese people had severely impaired responses after a 10% reduction in body weight.

“This was surprising,” said Mireille Serlie, MD, PhD, a professor of medicine endocrinology at Yale School of Medicine and senior study author. “We thought there would be different responses between lean people and people with obesity, but we didn’t expect this lack of changes in brain activity in people with obesity.”

After infusing glucose and fat into participants, it was observed that activity decreased in two parts of lean people’s brain striatum while only decreasing activity in one part of the striatum of obese people. Functionally, the striatum controls reward perception, motivation, and habit formation. Its decreased activity in lean people indicates that nutrient sensing is functioning correctly and preventing overeating.

A previous study from Yale researchers found that these cognitive changes may arise in early childhood. In that population-based analysis, scientists found that obese children had impaired brain development and that the networks responsible for cognitive control and decision-making were damaged.

The study authors suggest that more research is needed to fully understand the effect of weight loss on striatum activity and the possibility that a more significant percentage of body weight reduction could produce positive effects on reward-sensing activity.

Despite the evident relationship between brain health and obesity, it is unclear in which direction the causality flows or if there is a causal relationship between the two outcomes. In other medical research, experts have pointed to the environment as a determinant factor in obesity. A study from March of this year found that the type of food establishments surrounding a person’s residence are important factors influencing obesity. Specifically, communities without access to grocery stores or healthy food options often have higher obesity rates.

To limit the damage caused by obesity, pediatricians suggest that parents, teachers, and healthcare personnel prioritize early intervention. The American Academy of Pediatrics recommends that interventions focused on understanding and rectifying the complex causes of obesity can help families in the long run, reducing the likelihood of persistent obesity and its worst effects.