Older adults might want to try and lose a few inches off of their waistlines. A new study has associated a wider waist and higher body mass index to brain thinning.

The Waistline And The Brain

To look at the association between the size of the waistline and brain thinning, the researchers recruited 1,289 people. The participants had an average age of 64. About two-thirds of those who were involved in the study were Latino.

At the beginning of the study, the researchers measured the waist circumference of each participant and took note of their BMI.

A total of 346 participants had a BMI of less than 25, which is considered normal, 571 had 25 to 30, which means that they were overweight, and 372 had 30 or higher, which is categorized as obese. The normal weight group had an average of 33 inches waist circumference. Meanwhile, for the participants who were overweight, the average waist circumference was 36 inches. The average waist circumference among participants who were obese was 41 inches.

All participants underwent an MRI brain scan six years later. The findings were published in the online medical journal Neurology.

"People with bigger waists and higher BMI were more likely to have a thinning in the cortex area of the brain, which implies that obesity is associated with reduced gray matter of the brain," said Tatjana Rundek, a neurologist and one of the authors of the study, in a press release.

After adjusting for factors that might affect the results, researchers found a link between a higher BMI and thinner cortex. Every unit increase in BMI among overweight participants was associated with a 0.098-millimeter thinner cortex.  A wider waistline was also associated with the thinner cortex.

Wider Waistline Can Make The Brain Age Faster

The researchers noted that while brain thinning naturally occurs when people age, the process is quicker among those who are overweight and obese.

"In normal aging adults, the overall thinning rate of the cortical mantle is between 0.01 and 0.10 mm per decade, and our results would indicate that being overweight or obese may accelerate aging in the brain by at least a decade," explained Rundek.

Having a thinner cortex is also associated with an increased risk of Alzheimer's.

The researchers, however, warned that the study does not prove that having extra weight causes brain thinning.