It is pretty easy to gain weight as you grow older. Metabolisms slow, hormones shift, and people become generally less physically active more sedentary as they age. But inevitability doesn’t mean getting fatter doesn’t come with serious risks. Besides the increased likelihood of heart disease (the number one killer of men and women in America) gaining weight can do some serious damage to another arguably more essential organ — your brain. As bodies get bigger, a new study finds, brains actually shrink.
Cortical thinning, the phenomenon named in the study, refers to atrophy of the cerebral cortex, the part of the brain where almost all information processing occurs. The thinner the cortex, the greater the risk of Alzheimer’s and other neurological diseases. Scientists have understood that there is a link between healthy body weight and optimal brain health, but few studies have looked at the direct role weight might play. Based on what is already known about the cerebral cortex, study author and neurologist Dr. Tatjana Rundek believed that obesity could be connected to cortical thinning and overall brain atrophy.
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To test this, Rundek and her team recruited 1,289 people to compare their bodies and brains over time. At the start of the study, their BMI and waist circumference were measured and six years later, the participants’ brains were scanned using an MRI, in order to measure the thickness of the cortex and brain volume. Out of everyone, 571 people had BMIs in the 25 to 30 range, which is considered overweight, and 371 people were considered obese with BMIs 30 and higher. The higher the BMI, the thinner the cortex, results revealed. Even after Rundek controlled for variables that could change the cortex such as high blood pressure, alcohol use and smoking, every unit increase in BMI was linked with a 0.098 millimeter thinner cortex for overweight individuals and a 0.207 mm thinner cortex for obese ones.
“These associations were especially strong in those who were younger than 65, which adds weight to the theory that having poor health indicators in mid-life may increase the risk for brain aging and problems with memory and thinking skills in later life,” she warned. Having a larger waist was similarly associated with a thinner cortex, strengthening the link. To put it in perspective, in normal aging adults the overall thinning rate of the cortical mantle is between 0.01 and 0.10 mm per decade, but these findings indicate that being overweight or obese might speed up this process by another 10 years at least.
It is worth noting that the study demonstrates a correlation between weight and cortical thinning, but scientists are not at the point where they can confidently say putting on pounds causes brain thinning directly, or Alzheimer’s for that matter. The study also focused primarily on older participants with an average age of 64, but the data does give the younger man another reason to start and maintain healthy habits early on. It’s not just about looking good, it’s about having a big beautiful brain too.
“These results are exciting because they raise the possibility that by losing weight, people may be able to stave off aging of their brains and potentially the memory and thinking problems that can come along with brain aging,” Rundek said. “However, with the rising number of people globally who are overweight or obese and the difficulty many experiences with losing weight, obviously this is a concern for public health in the future as these people age.”
This article originally appeared on Fatherly. Follow @FatherlyHQ on Twitter.