After analyzing the results, they found a high BMI alone was linked to slightly lower brain volumes. They also said those with a high BMI and waist-to-hip ratio had lower gray matter, which is responsible for the parts of the brain that deal with self-control, muscle control and sensory perception.
In fact, the more than 1,200 people with a high BMI and belly fat had the lowest average gray matter brain volume, compared to those who didn’t have excess belly fat.
“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,” said Hamer. “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.”