Ashley May | USA TODAY

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Extra belly fat could be linked to a shrinking brain, according to a study published Wednesday.

Researchers measuring body mass index and waist-to-hip ratios found people with higher ratios of both had the lowest brain volume, according to a study published in an online issue of Neurology, the peer-reviewed medical journal of the American Academy of Neurology.

The study observed 9,652 people with an average age of 55. About 1,000 participants with high BMI and waist-to-hip ratios had the lowest average of gray matter in the brain, which controls self-control, muscle control and sensory perception, compared to about 3,000 participants of healthy weights who had an average amount of gray matter. About 500 participants with a high BMI but not a high waist-to-hip ratio also had an average amount of gray matter.

“It’s unclear if abnormalities in brain structure lead to obesity or if obesity leads to these changes in the brain,” study author Mark Hamer said in a statement. “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.”

Nastco, Getty Images/iStockphoto

The study was limited by participant size and health of participants, according to a news release. Only five percent of those invited to participate in the study took part, and that group tended to skew healthier. In other words, these results might not be true for the overall population. Chronic disease was also based on self-reporting physician diagnosis.

The research was conducted using the U.K. Biobank Resource and received funding from the National Institute for Health Research Leicester Biomedical Research Centre as well as the U.K. Medical Research Council and U.S. National Institute on Aging.