Being obese or underweight can increase the risk of Alzheimer's disease by 80pc, finds study

Obesity pushes up the risk of developing Alzheimer's by 80 per cent, claim researchers.

But being underweight can raise the chances of suffering any type of dementia around a third.

Latest evidence shows maintaining a healthy weight or even being slightly overweight is the best way to avoid an increased risk of mental decline in later years.

U.S. researchers carried out a review of ten international studies involving more than 37,000 people who were aged 40 to 80.

Researchers from the Johns Hopkins University in Baltimore, Maryland, and the University of Iowa, found obese people had a higher chance of dementia.

Dangerously overweight subjects were 42 per cent more likely to develop dementia.

When it came to Alzheimer's disease, obesity pushed up the risk by 80 per cent.

There was a stronger link between obesity and dementia in studies with a follow-up of more than ten years and among those who suffered mental decline before they reached 60.

Overall, 2534 people across the studies had dementia, according to the review, published yesterday in the journal Obesity Reviews.

Experts do not know how obesity affects the risk of dementia, although hardening of the arteries and high blood pressure may play a role.