Researchers at the University of Cambridge are warning that being overweight in middle age may age your brain by 10 years. 
The Study and the Findings
A team of researchers from the Cambridge Center for Aging and Neuroscience looked at the brains of 473 people between the ages of 20 and 87, and divided them into two categories: lean and overweight.
The white matter of the brain is the tissue that connects areas of the brain and allows for the exchange of information between regions. The white matter of those in the overweight category, defined as having a body mass index (BMI) above 25, had shrunk considerably more than it had in the brains of those in the lean category.
Brain shrinkage is associated with a higher risk of cognitive decline and dementia. 
The researchers scanned the participants’ brains and discovered changes in the brain structure of overweight people that are normally seen in people of advanced age.
The team calculated how white matter volume related to age across the two groups and found that at age 50, overweight people had as much white matter volume as a 60-year-old. 
Lead researcher, Dr. Lisa Ronan from the Department of Psychiatry at the University of Cambridge, said:
“We found that those who were overweight had significantly smaller volume of white matter compared with their lean counterparts – amounting to a difference of 10 years.” 
However, the difference between the brains of those in the overweight category and those in the lean category was only apparent from middle age on. Paul Fletcher, one of the researchers, said it could be that people are particularly vulnerable to these changes during that period of life. 
Fortunately, being overweight did not appear to be associated with reduced brain function during middle age.
But previous research has linked excess weight with cognitive decline later in life.
In 2012, a Swedish study that followed 9,000 twins for 30 years found that twins who were overweight or obese during middle age had an 80% higher risk of developing dementia compared to those who were of normal weight.
What the Findings Mean
Researcher Sadaf Farooqi said:
“We don’t yet know the implications of these changes in brain structure.” 
“It will be important to find out whether these changes could be reversible with weight loss, which may well be the case.” 
“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.” 
There is already some evidence that weight loss might improve memory and overall brain health.
Scientists at Kent State University in 2011 studied 100 people with an average weight of 300 pounds. Of that number, 109 people decided to undergo some type of weight loss surgery, while the remaining 41 people did not.
Twelve weeks later, the researchers conducted memory tests and found that the surgery group – which had lost an average of 50 pounds – improved in many of the tests, including memory and executive functioning.
The participants who opted out of weight loss surgery actually showed a small decline in memory and overall brain health.
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