By Dennis Thompson
Overweight and obese children tend to have a thinner prefrontal cortex, a part of the brain associated with decision-making and problem-solving. These same kids performed more poorly on games designed to evaluate those skills, said lead researcher Jennifer Laurent. She is an associate professor with the University of Vermont College of Nursing and Health Sciences, in Burlington.
"With escalating levels of BMI [body mass index], there was reduction in all of the cortical areas but specifically in the prefrontal cortex," Laurent said. "In that situation, these kids had a poorer working memory. Working memory is what you use to make decisions."
There are 13.7 million children and teens in the United States who are obese, and another 12 million are overweight, the researchers said in background notes.
Previous studies have associated childhood obesity with early risk of heart disease and type 2 diabetes, Laurent added.
So, the researchers gathered data from a large-scale study of adolescent brain development, which recruited a large number of 9- and 10-year-old children at 21 sites across the United States in 2017.
Nearly 3,200 children were weighed and then given a battery of thinking and memory tests. The kids also underwent an MRI brain scan.
About 13% of the kids qualified as overweight and 15% were obese, the researchers said.
As BMI increased, the outer layer of the brain -- the cortex -- became thinner in these kids, brain scans revealed.
The effect was particularly apparent in the prefrontal cortex, which is at the front of the brain and is the last part of the cortex to develop in children, Laurent said.
"That's one of the reasons adolescents are so impulsive, it's because their prefrontal cortex isn't fully developed," Laurent said. "They don't have that ability to walk away from something."
Brain games showed an association between a thinner prefrontal cortex and poorer ability to reason, organize information, and decide.
The findings were published online Dec. 9 in JAMA Pediatrics.
Because this was an observational study that did not prove cause and effect, it's hard to say exactly how the association between weight and brain structure works, Laurent said.
It could be that obesity causes a thinner cortex, or it could be that a thin cortex leads to poor decision-making that causes obesity, she explained.
"Perhaps these particular children are making less appropriate decisions about what they eat or when they eat or how they eat," Laurent said. "We really don't know.
However, these results should serve as a wake-up call regarding the need to prevent childhood obesity, she added.
"Kids as early as 10 years old may be having metabolic dysfunction that's affecting their heart and their brain," Laurent said. "It hopefully is a public health alert that we really need to start addressing healthy eating behaviors and other healthy behaviors really early in life."
However, Laurent warned that these findings should not be used to contribute to any sort of fat-shaming.
"We don't want people to think if kids are obese, that they have a problem with their brain or that they're stupid," Laurent said. "It doesn't have anything to do with their intellectual capability."
Childhood obesity expert Dr. Eliana Perrin, who co-wrote an editorial accompanying the study, agreed with Laurent.
"I am definitely concerned that these findings could be used out of context to further stigmatize children and adolescents with obesity, and that stigma we know is very harmful," said Perrin, director of the Duke University Center for Childhood Obesity Research in Durham, N.C.
Perrin added that there might even be some as-yet-unknown additional factor that's influencing the kids' weight, brain structure, performance on brain games, or all three.
"Sometimes when people see that one thing happens alongside another thing, they think that first thing caused the other when we don't know that at all," Perrin said. "In research, this work is often stepwise. It's important that we not turn it into something it's not before we've completed all the steps."