Men with beer bellies and women with “muffin tops” have smaller brains, suggests a new study.
Researchers found that carrying extra body fat, especially around the waist, may be linked to brain shrinkage.
They calculated obesity by measuring body mass index (BMI) and waist-to-hip ratio in study participants.
The findings, published online by the journal Neurology, show those with higher ratios of both measures had the lowest brain volume.
Study author Professor Mark Hamer, of Loughborough University, 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.”
BMI is a weight-to-height ratio. It is determined by dividing a person’s weight by the square of their height. People with a BMI above 30 are considered obese.
Waist-to-hip ratio is determined by dividing waist circumference by hip circumference. People with bigger bellies compared to their hips have higher ratios. Men above 0.90 and women above 0.85 are considered to be centrally obese.
The study looked at 9,652 people with an average age of 55. Of that group, 19 percent were determined to be obese.
Researchers measured BMI, waist-to-hip ratio and overall body fat and surveyed the participants about their health.
They then used MRI scans to determine brain volumes for white and gray brain matter and volumes in the various regions of the brain.
Gray matter contains most of the brain’s nerve cells and includes brain regions involved in self-control, muscle control and sensory perception.
White matter contains nerve fiber bundles that connect various regions of the brain.
After adjusting for other factors that may affect brain volume – such as age, physical activity, smoking and high blood pressure, the researchers found that while a high BMI alone was linked to slightly lower brain volumes, those with high BMI and waist-to-hip ratios had lower gray matter brain volumes than those who didn’t.
They found that 1,291 people who had a high BMI and a high waist-to-hip ratio had the lowest average gray matter brain volume of 786 cubic centimeters, compared to 3,025 people of healthy weight who had an average gray matter brain volume of 798 cubic cms and 514 people with a high BMI but without high waist-to-hip ratio who had an average gray matter brain volume of 793 cubic cms.
They found no significant differences in white matter brain volume.
Prof Hamer added: “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.”