Gorging on junk food may not just make you fat – it could also give you dementia.

Evidence is growing that a bad diet triggers Alzheimer's by poisoning the brain.

With studies on animals strongly implicating the hormone insulin in the process, some believe Alzheimer's to be another version of diabetes.

Bizarre as the claim may seem, confirming the link could speed the search for desperately needed new treatments for Alzheimer's, which, along with other forms of dementia, affects more than 800,000 Britons.

Bad diets are already linked to dementia, through high blood pressure and cholesterol interrupting blood supply to the brain.