Being overweight associated with reduced white matter volume

By Sally Robertson, B.Sc.Aug 11 2016

From middle-age onwards, the brains of people who are obese or overweight exhibit differences in white matter similar to lean individuals who are 10 years their senior, according to researchers from the University of Cambridge.

Brain scans showed overweight and obese people had a greater shrinkage in the volume of white matter, although their cognitive performance did not seem to be affected.

The overall message is that brains basically appear to be 10 years older if you are overweight or obese,”

Lisa Ronan, lead author of the study.

White matter is the tissue made up of nerve fibers that connects brain areas and allows for information to be communicated between different brain regions.

The volume of this white matter decreases with age in all individuals, but it is not clear why overweight people have a greater reduction than lean individuals.

Ronan and team looked at data for 473 people aged between 20 and 87 and investigated the impact of obesity on brain structure across the adult lifespan.

When they divided the data into two categories, lean and overweight, they found that overweight people had a more widespread reduction in white matter, compared to lean people.

As reported in Neurobiology of Aging, the researchers calculated how age and the volume of white matter were related across the two groups.

They found that an overweight person, aged 50 years, for example, had a white matter volume that was comparable to that of a lean individual aged 60 years, therefore suggesting a ten-year difference in brain age.

Interestingly, the researchers found that the difference was only observed for people who were middle-aged or older, implying that the brain may be especially vulnerable from middle-age onwards.

We’re living in an ageing 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, Co-author.

Despite overweight being associated with a reduced white matter volume, this did not seem to have any effect on cognitive ability, with no difference seen between lean and overweight individuals when they took a standard test similar to an IQ test.

Co-author Sadaf Farooqi says: “We don’t yet know the implications of these changes in brain structure. Clearly, this must be a starting point for us to explore in more depth the effects of weight, diet and exercise on the brain and memory.”

Ronan says that further research is needed to look at the influence of BMI-linked brain ageing on neurodegenerative illness because the findings raise the possibility that overweight and obesity is associated with the age-related decline seen in Alzheimer’s and dementia.