11/08/2016 7:56 AM AEST | Updated 12/08/2016 12:47 AM AEST

Being Overweight Can Age Your Brain Up To 10 Years

It has to do with the brain’s white matter.

For those who are overweight around age 40, brain aging may be more advanced than it is in lean peers, according to a recent study published in the journal Neurobiology of Aging.

The study’s results revealed that middle-age individuals who were overweight or obese had significantly “older looking” brains, as defined by less white matter.

White matter, which has been called the “subway of the brain,” allows long-range connections, linking brain regions together, according to the study’s author, Lisa Ronan. This allows the brain to transmit messages quickly and operate as efficiently as possible. White matter begins to naturally decrease around age 40, but the study’s data showed a more significant decrease for overweight and obese individuals around this age.

The study included MRI-based data from 473 individuals between the ages of 20 and 87. Researchers from the University of Cambridge identified differences in brain structure for each subject and found that overweight and obese individuals around age 40 had significantly smaller white matter volumes.

“We found that this difference in volume equated to a brain-age increase of 10 years in the overweight/obese group,” said Ronan.

“The fact that we only saw these differences from middle-age onwards raises the possibility that we may be particularly vulnerable at this age,” senior study author Paul Fletcher added 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.”

Lisa Ronan
Comparison of grey matter (brown) and white matter (yellow) in sex-matched subjects A (56 years, BMI 19.5) and B (50 years, BMI 43.4).

For the study, the subjects were divided into two categories: lean (a BMI between 18.5 to 25) and overweight/obese (a BMI greater than 25). The researchers compared white matter volume between the brains of age-matched individuals to find the difference. 

Though the white matter volumes equated to a brain-age increase of 10 years for these individuals, Ronan emphasized that the researchers found no evidence of an impact on cognitive ability. 

The researchers also found no similar changes in the grey matter of the brain, which contains the majority of neurons and is responsible for basic functions of the brain, including memory, speech, motor control and sensory perceptions.

Lisa Ronan
Age-trajectory of white matter volume for lean (BMI 18.5 - 25) and overweight (BMI 25 - 30) and obese (BMI > 30).

We still don’t know what this means

As for the larger implications of the study, it is simply too early to tell. A reduction of white matter due to excess weight could put individuals at risk for neurological disorders, but more research needs to be conducted to make that conclusion, Ronan said.

“It is possible that being overweight may raise the risk of developing disorders related to neurodegeneration such as Alzheimer’s disease or dementia,” she said, but emphasized that this study didn’t investigate, nor did it find such a correlation.

Overweight and obese individuals have been shown to have an increased risk for diabetes, cancer and heart disease, but evidence showing a correlation between weight and brain aging is minimal.

The most important and immediate takeaway from the research is that there may be a connection between weight and brain degeneration. That could have potentially scary outcomes for brain health, especially as obesity rates continue to rise.

“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,” Fletcher said.