Excess pounds in kids can be a bane to brain health

Children with overweight or obesity appear to exhibit alterations in brain structure and function that can be detrimental to cognitive function and school performance, according to data from the Adolescent Brain Cognitive Development (ABCD) study.

Higher weight and body mass index (BMI) in 9- to 10-year-olds were associated with poor brain health, said lead study investigator Simone Kaltenhauser, a postgraduate research fellow at the Yale School of Medicine in New Haven, Connecticut, US. Kaltenhauser presented the results at the annual meeting of the Radiological Society of North America (RSNA).

Imaging data from 11,878 children (51.9 percent girls) participating in the ABCD study showed significant brain abnormalities at higher weight and BMI z-scores. For the most part, there was significant impairment to the integrity of the white matter. [RSNA 2022, abstract M6-SSNR05-1]

Fractional anisotropy (FA) reductions were most pronounced in the corpus callosum (p<0.00000001), fornix (p<0.000001), and (parietal and temporal) superior longitudinal fasciculus (p<0.001)—parts of the brain that facilitate communication between the left and right hemispheres, connect the lobes, and play a key role in cognition and episodic memory recall, respectively. [J Neurol Neurosurg Psychiatry 2020;91:547-559]

“It is striking that these changes were visible early on during childhood,” Kaltenhauser said.

She also pointed out other important findings such as the thinning of the cortical grey matter and decreased connectivity in the functional networks of the brain involved in cognitive control, motivation, and reward-based decision making.

“We expected the decrease in cortical thickness among the higher weight and BMI z-score children, as this was found previously in smaller subsamples of the ABCD study,” Kaltenhauser noted. “However, we were surprised by the extent of white matter impairment.”

The takeaway is that overweight and obesity not only pose physical health consequences but also exert harmful effects on brain health, she said.

In ABCD, 21.0 percent of the children were overweight while 17.6 percent were obese. None of the children had eating disorders, neurodevelopmental and psychiatric diseases, and traumatic brain injury. All of them underwent structural magnetic resonance imaging (MRI) and resting-state functional MRI.

Adopting an active lifestyle

While the ABCD study offers no clues as to whether losing weight would reverse the brain abnormalities, a recent review has reported that physical activity has the potential to modulate the associations among childhood obesity, cognitive abilities, and the structure and activity of the brain. [Front Neurosci 2022;doi:10.3389/fnins.2022.1019129]

Several MRI studies have shown increases in white matter integrity in overweight children after a long-term physical exercise intervention or motor training. However, these studies could not tell whether the changes in white matter integrity were due to complex motor skill training or improved physical fitness.

Also, the exact duration of the beneficial effects of physical exercise for overweight and obese children is unclear. This highlights the need to conduct more studies to examine whether the effects of exercise on brain structure and function are short term or sustained in the long term.

“Childhood is a sensitive period for brain and cognitive development, and both physical activity and exercise are beneficial for children regardless of their weight status. Exercise can help children maintain a healthy weight and even attenuate the alterations of brain and cognition caused by obesity,” according to the authors of the review.

“We suggest that children, especially those with obesity, increase their daily physical exercise, decrease sedentary behaviour, and develop an active lifestyle. Overall, exercise should be a regular activity for children, and establishing an enjoyable exercise routine may help in the long term,” they added.