A new study led by researchers at Leiden University Medical Center in the Netherlands suggests that obesity may be associated with changes in brain structure, including reduced brain volumes in certain areas.
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The research team analyzed magnetic resonance imaging (MRI) scans and found that higher levels of body fat were associated with reduced volumes of gray matter and an increased likelihood of changes in the white matter.
As reported in the journal Radiology, the study also found that the association was stronger among men, compared with among women.
Higher levels of fat distributed over the body is associated with smaller volumes of important structures of the brain, including grey matter structures that are located in the center of the brain.”
IIona Dekkers, Lead Author
“Interestingly, we observed that these associations are different for men and women, suggesting that gender is an important modifier of the link between fat percentage and the size of specific brain structures.”
The study adds to the growing body of evidence suggesting that obesity is associated with changes in brain structure. Previous research has also demonstrated a link between obesity and an increased risk for accelerated cognitive decline and brain diseases such as dementia.
Obesity changes the structure of the brain
Previous studies tended to be small and only used indirect measures of body fat such as body mass index (BMI) and waist-to-hip ratio.
For the current study, Dekkers and team analyzed MRI scans available for 12,087 participants (aged an average of 62 years) from the UK Biobank study and assessed the gray- and white-matter structure of their brains. They also measured the participant's levels of body fat using a method called bioelectrical impedance, which provides an estimate of body fat percentage.
The researchers found that among men, an increased body fat percentage was associated with a lower overall volume of gray matter — the brain tissue that contains nerve cells.
It was also associated with reduced grey matter volumes in areas within the center of the brain, including the thalamus, hippocampus, and caudate nucleus. Some of these brain regions are involved in the regulation of body movement, while others are involved in the brain’s reward circuit.
Among women, the team only found an association between increased body fat and reduced gray matter volume in a region called the globus pallidus, which is involved in the regulation of voluntary body movement.
Among both men and women, a higher total body fat percentage was associated with an increased likelihood of microscopic changes in the brain’s white matter – the long nerve fibers that enable communication between different brain regions.
Understanding the effect of poor health on the brain
Commenting on the value of MRI, Dekkers refers to the technique as an irreplaceable tool for understanding the link between neuroanatomical differences of the brain and behavior:
Our study shows that very large data collection of MRI data can lead to improved insight into exactly which brain structures are involved in all sorts of health outcomes, such as obesity.”
However, the authors note that the study has only revealed associations between body fat levels and reduced brain volume, so cannot be taken as proof that excess body fat actually causes brain shrinkage.
They say further studies are needed to examine the association and to establish whether weight loss could be beneficial to brain health.