Toronto, July 1 (IANS): While ageing has been long identified as a significant risk factor for Alzheimer's disease, a new study shows that obesity during middle age may contribute to the early development of the brain disorder, termed as the most common form of dementia.

The results showed that ageing, combined with a high fat and high sugar diet, results in increased inflammation and stress in the hippocampus -- responsible for long-term memory -- and prefrontal cortex -- responsible for complex cognitive, emotional and behavioural function.

Both brain regions are thought to be involved in the progression of Alzheimer's disease.

"This study provides novel information in relation to the mechanistic link between obesity and the transition from adulthood to middle age and signalling cascades that may be related to (Alzheimer's) pathology later in life," said researchers, including Rebecca E.K. MacPherson, from the Brock University in Ontario, Canada.

In the study, published in the journal Physiological reports, the team used a mouse model to look at the effects of an obesity-inducing diet on insulin signalling -- the process that tells the body how to use sugar -- and markers of inflammation and cellular stress.

One group of mice received a high-fat, high-sugar diet ("HFS"), while the control group had a normal diet.

Mice with HFS demonstrated significantly higher markers of inflammation, insulin resistance and cellular stress in areas of the hippocampus thought to be involved in the progression of Alzheimer's disease.

The study also revealed that certain areas of the brain respond differently to risk factors associated with Alzheimer's.

"These results add to our basic understanding of the pathways involved in the early progression of (Alzheimer's) pathogenesis and demonstrate the negative effects of a HFS diet on both the prefrontal cortex and hippocampal regions," MacPherson said.