Brains of obese or overweight people appear to have aged an extra 10 years compared to their lean peers from middle age on, research has revealed.
The difference, say the Cambridge and Yale scientists who conducted the study, corresponds to a greater shrinkage in the volume of white matter.
They don’t know the cause. It might be down to genes causing both brain-shrinking and obesity, or it could be that changes occurring in the brain lead to overeating.
Either way, it does not appear to affect mental performance. There was no difference between lean and overweight or obese participants in IQ tests.
“The overall message is that brains basically appear to be 10 years older if you are overweight or obese,” said Lisa Ronan of the University of Cambridge.
“This study raises the possibility that if you are overweight or obese you may be more susceptible to diseases [linked] to age-related decline such as dementia and Alzheimer’s.
“The jury is still out regarding any potential links between obesity and risk of memory loss and dementia – but we do know that what is good for the heart is also good for the head. Evidence shows that the best ways to reduce your risk of dementia include following a healthy diet, taking plenty of exercise and stopping smoking,” she said.
White matter is tissue, composed of nerve fibres, that aids communication between different regions of the brain. The volume of white matter in a human brain increases during youth and then decreases with age for both lean people and those who are overweight or obese.
The scientists sought to unpick links between obesity and brain structure by analysing MRI scans from 473 people aged between 20-87.
The researchers split the participants into two categories based on their BMI, with 246 classified as lean and 227 as overweight or obese.
They analysed the brain scans for the two groups, taking into account gender and various self-reported health issues such as high blood pressure and diabetes, to create a computer model that explored how the volume of white matter changed with age among the participants.
When the researchers looked at those over 37 – the age at which the volume of white matter starts to decrease – they discovered those who were overweight or obese had a smaller volume of white matter than who were lean. This difference was greatest around the age of 40 and then stabilised, corresponding to an increase in brain age of around a decade compared to lean participants.