People who carry extra body fat around their bellies have smaller brains, new research concludes.
The study of almost 10,000 people found that those who have higher body-mass indexes and larger waists have less gray matter.
Brain shrinkage is linked to a higher risk of dementia and memory problems.
The study suggests that people with a healthier weight likely have more gray matter and, therefore, healthier brains.
Dr Mark Hamer, the study’s first author, said:
“Existing research has linked brain shrinkage to memory decline and a higher risk of dementia, but research on whether extra body fat is protective or detrimental to brain size has been inconclusive.
Our research looked at a large group of people and found obesity, specifically around the middle, may be linked with brain shrinkage.”
The study included 9,652 people, of whom 19% were obese.
They were given brain scans and their body fat was assessed.
The results showed that those with more body fat had less ‘gray matter’ in their brains.
Gray matter refers to brain cells, along with their accompanying structures: the part of the brain that processes information.
Dr Hamer said:
“While our study found obesity, especially around the middle, was associated with lower gray matter brain volumes, it’s unclear if abnormalities in brain structure lead to obesity or if obesity leads to these changes in the brain.
We also found links between obesity and shrinkage in specific regions of the brain.
This will need further research but it may be possible that someday regularly measuring BMI and waist-to-hip ratio may help determine brain health.”
People with BMIs over 30 are considered obese (search online for a BMI calculator).
Men with waist-to-hip ratios of 0.9 or greater are considered centrally obese.
The figure for women is 0.85.
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The study was published in the journal Neurology (Hamer & Batty et al., 2019).