The brains of middle-aged, overweight people look 10 years older when compared to those of their lean counterparts.

Human brains naturally shrink with age, but a new study found that being overweight may affect the onset and progression of brain ageing. The results were found by comparing the white matter volume in brains of overweight and lean people.

According to the study, an overweight person at age 50 had white matter volume comparable to that of a lean 60-year-old, implying a difference in brain age of 10 years. However, direct studies to support this link are lacking.

“As our brains age, they naturally shrink in size, but it isn’t clear why people who are overweight have a greater reduction in the amount of white matter,” Dr Lisa Ronan, the first author from the Department of Psychiatry at the University of Cambridge, said.

“We can only speculate on whether obesity might in some way cause these changes or whether obesity is a consequence of brain changes.”

“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,” senior author Professor Paul Fletcher, from the Department of Psychiatry, adds.

“The fact that we only saw these differences from middle-age onwards raises the possibility that we may be particularly vulnerable at this age. It will also be important to find out whether these changes could be reversible with weight loss, which may well be the case.”

Although the differences in the white matter volume between lean and overweight people are clear, the researchers did not find a connection between being overweight or obese and an individual’s intelligence, as measured using a standard test similar to an IQ test.

The study is a starting point in in-depth exploring the effects of weight, diet and exercise on the brain and memory, the researchers said.

The team studied data from 473 individuals between the ages of 20 and 87. The results are published in the journal Neurobiology of Aging.