Unhealthy diets have already been linked to dementia due to high blood pressure and cholesterol disrupting the brain, but research now suggests it can also stop brain cells responding properly to insulin.

Too much fatty and sweet food can increase insulin levels causing fat, muscle and liver cells to stop responding to the hormone, Medical Daily explained.

When the brain stops responding to insulin, humans' capacity to think and create new memories is hindered, according to the paper recently published in New Scientist magazine.

Researchers at Brown University, led by Dr Suzanne del Monte, conducted lab tests on rats. They found blocking insulin from the brain caused confusion. Further investigation showed similar patterns as Alzheimer's disease.