IF you’re too heavy, especially around your middle, you probably have shrunken gray matter volume in your brain, according to a study published in the journal Neurology. Gray matter contains most of your brain’s 100 billion nerve cells, while white matter is filled with nerve fibers that connect the brain regions.

“Previous studies have shown associations between gray matter atrophy and risk of developing dementia,” study author Mark Hamer, a professor of exercise as medicine at Loughborough University in England, wrote in an email.

The study of 9,652 middle-aged people in the U.K. measured body mass index (BMI) and waist-to-hip ratio. BMI is a formula involving a person’s weight and height; a BMI score between 18.5 and 24.9 is considered healthy, while above 30 is considered obese. Similarly, the waist-to-hip ratio is scored, and a high score — above 0.90 for men and above 0.85 for women — means a person has central obesity, or a bigger belly than hips.

Based on these criteria, nearly one in five of the study participants was found to be obese.

Hamer and his co-researchers also used an MRI to scan participants’ brain volume. The researchers factored in age, physical activity, smoking and high blood pressure, all of which might lead to reduced volume.

What did they find? People with higher numbers on both BMI and waist-to-hip ratio had the lowest gray matter volume. “The reductions in brain size increase in a linear fashion as fat around the middle grew larger,” Hamer wrote.

The study also showed no real differences in white matter brain volume linked to obesity. However, excess weight was associated with shrinkage in specific regions of the brain: the pallidum, nucleus accumbens, putamen (linked only to a higher BMI) and caudate (linked only to a higher waist-to-hip ratio). All of these brain regions are involved in motivation and reward.

(SD-Agencies)