Being obese is bad for a child’s brain as well as their physical health, a new study reveals.
Higher weight and body mass index (BMI) before adolescence are associated with poor brain health, researchers have found.
They observed structural brain changes in overweight boys and girls aged nine and 10, including “significant impairment” to the integrity of the white matter.
The team used MRI scan data from the biggest long-term study of brain development and child health in the United States.
Researcher Simone Kaltenhauser said: “We know being obese as an adult is associated with poor brain health.
“However, previous studies on children have often focused on small, specific study populations or single aspects of brain health.”
Childhood obesity is a growing concern with around one in seven children aged four or five in the UK obese (14.4 per cent), while one in four youngsters aged 10 or 11 are clinically obese (25.5 per cent), according to official statistics.
The new study used imaging data from the Adolescent Brain Cognitive Development (ABCD) study that included more than 11,800 children nine or 10-years-old from 21 centres to represent the sociodemographic diversity of the United States..
Ms Kaltenhauser, a post-graduate research fellow in radiology and biomedical imaging at Yale School of Medicine, said: “This dataset is unique in that it closely approximates the US population.”
After excluding children with eating disorders, neurodevelopmental and psychiatric diseases, and traumatic brain injury, the study group included 5,169 children.
According to the children’s BMI z-scores - measures of relative weight adjusted for a child’s age, sex and height - the overweight and obesity rates within the study group were 21 per cent and 17.6 per cent, respectively.
To gain a comprehensive view of brain health, the researchers evaluated information from structural MRI and resting-state functional MRI (fMRI), which enables them to measure brain activity by detecting changes in blood flow.
With resting state fMRI, the connectivity between neural regions - known as resting state networks - can be observed while the brain is at rest.
The research team also evaluated data from diffusion tensor imaging - a technique that helps assess white matter - and restriction spectrum imaging, an advanced diffusion MRI technique.
After correcting for age, sex, race-ethnicity, handedness and socio-economic status, the research team used models to determine associations between weight and BMI z-scores and the imaging metrics.
They observed structural brain changes in children with higher weight and BMI z-scores, including “significant impairment” to the integrity of the white matter.
Areas of degradation included the white matter of the corpus callosum, the principal connector between the brain’s two hemispheres, and tracts within the hemispheres that connect the lobes of the brain.
Ms Kaltenhauser said: “It is striking that these changes were visible early on during childhood.”
The research team also observed a thinning of the outermost layer of the brain, or the cortex, which has been associated with impaired executive function.
Ms Kaltenhauser said: “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.
“However, we were surprised by the extent of white matter impairment.”
Resting-state fMRI images revealed that increased weight and BMI z-scores were associated with decreased connectivity in the functional networks of the brain that involve cognitive control, motivation and reward-based decision making.
Ms Kaltenhauser said: “Increased BMI and weight are not only associated with physical health consequences but also with brain health.”
She added: “Our study showed that higher weight and BMI z-scores in nine- and 10-year-olds were associated with changes in macrostructures, microstructures and functional connectivity that worsened brain health.”
Study senior author Doctor Sam Payabvash says the study’s findings provide an “important mechanistic explanation” of other studies that show higher BMI in children is associated with poor cognitive functioning and school performance.
Dr Payabvash, a neuroradiologist and Assistant Professor of radiology and biomedical imaging at the Yale School of Medicine, said: “The longitudinal ABCD study gives us the opportunity to observe any changes that occur in children with higher weight and BMI z-scores.”
He added: “We’ll need to watch over the next six to 10 years.”
The findings were presented at the annual meeting of the Radiological Society of North America (RSNA) in Chicago.
