Brains in the obese had an average of eight per cent less tissue and had aged prematurely by 16 years
Overweight people have smaller brains and are more at risk of Alzheimer's, according to a study.
Their brains also age faster than those of slim people.
Researchers found that brains in the obese had an average of eight per cent less tissue and had aged prematurely by 16 years, while those in the overweight had 4 per cent less tissue and appeared eight years older.
The study is the first to find a link between weight and brain function.
Researchers compared brain scans of 94 people in their 70s who were obese, overweight or of normal weight. They found that the obese had lost tissue in the frontal and temporal lobes - areas critical for planning and memory.
Declines were also seen in areas used for attention and executive functions, longterm memory and movement. Professor Paul Thompson, a neurologist and one of the researchers, said: 'That's a big loss of tissue and it depletes your cognitive reserves, putting you at much greater risk of Alzheimer's and other diseases that attack the brain.
'But you can greatly reduce your risk for Alzheimer's if you can eat healthily and keep your weight under control.'
The World Health Organisation says there are more than 300million obese people around the world, with a billion more overweight. They are at increased risk of heart disease, diabetes and high blood pressure.
Co-researcher Cyrus A. Raji, a medical student at the University of Pittsburgh, said: 'It seems along with increased risk for health problems such as type 2 diabetes and heart disease, obesity is bad for your brain.
'We have linked it to shrinkage of brain areas that are also targeted by Alzheimer's.'
