Structural differences in brain found in obese children

Overweight, obese children aren't only prone to future health risks but their brain structure has been found to have differences in regions linked to cognitive control, compared to those with normal weight.

However, researchers stated that it was hard to say if obesity caused these changes or whether the children are obese because their brain structures are different, according to a study published in the journal Cerebral Cortex.

Previous studies have linked being overweight with scoring lower on various measures of executive function, an umbrella term for several functions such as self-control, decision making, working memory (temporarily holding information for processing) and response to rewards.

To examine if this link existed in children, researchers analysed data from 2,700 children between the ages of 9-11 years who had been recruited as part of the National Institutes of Health Adolescent Brain Cognitive Development (NIH ABCD) Study.

They observed the thickness of the cortex, the outer layer of the brain - our so-called 'grey matter' - and compared it to each child's body mass index (BMI) and also analysed results from tests of executive function.

An association between increased BMI and significant reductions in the average (mean) thickness of the cortex, as well as thinning in the pre-frontal region of the cortex, an area associated with cognitive control; was found.

This relationship remained after accounting for factors including age, sex, race, parental education, household income and birth-weight.

Researchers also found that increased BMI was associated with poorer performance at tests to measure executive function.

"We saw very clear differences in brain structure between children who were obese and children who were a healthy weight," said study's first author Dr Lisa Ronan from the Department of Psychiatry at the University of Cambridge.

"It's important to stress that the data does not show changes over time, so we cannot say whether being obese has changed the structure of these children's brain or whether innate differences in their brains lead them to become obese," Dr Ronan added.

When the team used waist circumference and waist-to-height ratio as a measure of obesity, they found that these, too, were associated with reduced executive function, but the link between cortical thickness was more complicated, with some regions showed reduced thickness while others showed increased thickness.

"The links that we observed suggest that there are very real structural brain and cognitive differences in children who are obese. The findings contribute a small part towards our growing understanding of the causes and consequences of obesity in children," added Professor Paul Fletcher, also at Cambridge's Department of Psychiatry.

Researchers will continue following these children as they grow older to see whether structural differences in the brain change over time and exactly how they relate to obesity.