The brains of middle-aged overweight people appear 10 years older than those of their normal-weight peers, according to new research. The loss of white matter—tissue that allows for communication between different areas of the brain—is a normal part of aging, say the authors of the new study. But their imaging scans showed that heavier participants experienced widespread loss about a decade earlier than leaner ones.
While the study did not find a connection between participants’ weight and cognitive abilities, the authors do say that their results raise concerns about obesity’s possible role in age-related brain disease.
To compare the brains of different-weight individuals, researchers from the University of Cambridge in the U.K. performed MRIs on 473 study participants between ages 20 and 87. When they divided the results into two categories—lean and overweight or obese—they found a striking difference between the groups.
Overweight people (those with a body mass index of 25 or higher) had significantly less white matter compared to lean people. In fact, the authors noted, the effect looked a lot like what would happen with normal aging, only accelerated. When they calculated the differences across age groups, their observation was confirmed: An overweight 50-year-old, for example, had comparable white matter to a lean 60-year-old.
The differences between groups only appeared in people who were middle-aged and older, suggesting that the brain may be particularly vulnerable to obesity-related damage during this period of life.
The study did not, however, find any difference in cognitive function between the two groups. (In addition to MRIs, participants were given a standard questionnaire similar to an IQ test.) Lead author Lisa Ronan, Ph.D., says this is an important caveat in their results.
“Until we can unpack what is going on, it would be too soon to be alarmist about our findings,” she says. “That being said, it is reasonable to wonder whether an increased BMI may also increase the risk for developing age-related neurodegenerative disorders such as Alzheimer’s disease and dementia.”
And for people who were overweight and had significant loss of white matter, the study wasn’t able to show which came first. “We can only speculate on whether obesity might in some way cause these changes or whether obesity is a consequence of brain changes,” Ronan says.
Based on the results of this study, she adds, there’s no reason for adults (of any weight) to consider getting a brain scan. It does, however, suggest another potential way that extra pounds might be bad for our health—and another reason to aim for or maintain a healthy weight.
The study’s senior author agrees that there’s still a lot to learn in this area. “We’re living in an aging population, with increasing levels of obesity, so it’s essential that we establish how these two factors might interact, since the consequences for health are potentially serious,” Paul Fletcher, Ph.D., said in a press release. “It will also be important to find out whether these changes could be reversible with weight loss, which may well be the case.”