Research from the Australian National University (ANU) is warning of a link between the extra calories in a fast-food burger and brain diseases, including dementia.

People are "eating away at their brain with a really bad fast-food diet and little to no exercise," the lead author of the study said. The ANU study also reinforces the link between type 2 diabetes, which is often triggered by obesity, and the rapid deterioration of brain function.

Dementia is the leading cause of death in Australian women, while for men it is second only to heart disease.

A clear link

Researchers believe there is a clear link between the deterioration of the brain and an unhealthy diet as well as a lack of exercise. There is a warning that highly processed fast food that is cheap, widely available and loaded with calories, sugar and fat is leading to significant harm.

The study from the ANU says that the damage to the brain is almost certainly irreversible once a person reaches middle age. Professor Nicolas Cherbuin says lifestyle choices really do matter.

"Poorer diet leads to the development of obesity," he said. "It is compounded by the lack of physical activity, it leads to an increased level of inflammation in our body, which when it is [in] response to trauma is a good thing. But when it is constantly there it creates damage. It also kills neurons, so it affects our brain function and it leads to ultimately a greater risk of developing dementia later in life."

A third of adults overweight, obese

The research says that about a third of the world's adult population is either overweight or obese. The advice is to eat well and exercise from a young age. It is estimated that dementia affects almost 50 million people worldwide, and the global cost of the brain syndromes, including Alzheimer's disease, is more than $800 billion.

At present there is no prevention or cure for most forms of dementia. However, some medication has been found to reduce some symptoms. (VOA)