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CHICAGO -- Children with overweight or obesity appeared to have abnormalities in the brain that could affect executive functioning, an analysis of data from the Adolescent Brain Cognitive Development (ABCD) Study showed.

Greater weight and body mass index (BMI) in typically developing 9- to 10-year-olds were associated with poor brain health, said Simone Kaltenhauser, PhD, a post-graduate research fellow at the Yale School of Medicine in New Haven, Connecticut, during the Radiological Society of North America (RSNA) annual meeting.

"At higher weight and body mass index, we found extensive alterations in brain health, including in the gray matter cortex and in white matter fiber tracts, as well as the functional coupling of brain units," Kaltenhauser told MedPage Today. "We were surprised these changes were visible so early on."

The researchers found that higher weight and BMI z-scores were associated with lower fractional anisotropy (FA) values in 16 and 25 white matter tracts, higher FA values in 1 and no tracts, lower axial diffusivity values in 23 and 30 tracts, higher radial diffusivity values in 5 and 10 tracts, lower radial diffusivity values in 3 and no tracts, lower neurite density values in 11 and 13 tracts, and higher neurite density values in 5 and 1 tracts, respectively.

For both weight and BMI z-scores, FA reductions were most pronounced in the corpus callosum, fornix, and superior longitudinal fasciculus (adjusted P<0.001 for all). For all tracts, higher radial diffusivity and lower axial diffusivity values were observed, which were significant for most of these regions of interest.

"Essentially our work provides an explanation for previous research that has shown that obesity measurements are associated with poor cognitive performance and academic achievement," she noted. "Because this is an ongoing longitudinal study, which has a total observational period of 10 years, we will be able to have a further look into this association in the future, and we will be able to determine more definite mechanistic links."

Kaltenhauser and colleagues used BMI as a continuous variable to assess overall brain health. "With higher weight, these brain metrics worsened," she said.

The analysis included 11,878 children ages 9 to 10 years from 21 centers across the country to represent the sociodemographic diversity in the U.S. After excluding children with eating disorders, neurodevelopmental and psychiatric diseases, and traumatic brain injury, the study group included 5,169 children (52% girls). Of these kids, 21% met the BMI criteria for overweight, and 17.6% met the criteria for obesity.

The current analysis looked at what has happened to the children as a group now that 2 years have passed, Kaltenhauser explained. Specifically, she and her team observed that with higher BMI, the children's brains had a lower cortical thickness, and integrity of white matter was also impaired.

With increased weight and BMI z-scores, the researchers observed thinning of 63 and 54 cortical regions, higher surface area of 52 and 26 cortical regions, and significant disruptions in 37 and 31 inter- and intra-network correlations, respectively.

The children in the study will undergo serial MRI every 2 years. "There are more data to come as we study these children, which will help us to draw definite conclusions," she added. "We will also have the opportunity to monitor the brain development over a longer period of time."

She said continuing the study will give the researchers a chance to determine if the brain changes being seen now are just artifacts of growing up or if they pose real brain health danger.

"We have seen that these brain health abnormalities did persist from baseline to 2 years, and we will be able to see if they continue to persist during the next round of magnetic resonance imaging," said Kaltenhauser, who will be continuing her medical studies at the University of Regensburg in Germany.

Max Wintermark, MD, chief of neuroradiology at the University of Texas MD Anderson Cancer Center in Houston, told MedPage Today, "I always wonder when I see these studies if it is because you are overweight that it is affecting the brain or if it is the lifestyle associated with weight gain that is causing the changes in the brain."

"It is not mentioned here, but the outstanding question is whether losing weight would reverse these brain changes," he added. "So, especially in the pediatric population, the question of reversibility of these brain changes needs to be explored."

Kaltenhauser noted that the ABCD Study is an observational study, and does not provide interventions. "We do not know what kinds of interventions, such as weight loss advice, [are] being provided by individual pediatricians," she said.

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