The research, led by Dr Olivier Piguet from Neuroscience Research Australia, shows for the first time that some people with frontotemporal dementia have deterioration in the brain region that controls hunger.
"We think the cells in this brain region lose the ability to tell these individuals when they've had enough to eat," says Dr Piguet.
These people become unable to control their urge to eat, gorging on sweet and carbohydrate-rich foods and eating in socially inappropriate ways, a situation which is unhealthy for the individual and highly distressing for the family.
"They may steal food from people’s plates or go looking for a bowl of sugar and eat the whole thing," says Dr Piguet. "Some people will even eat inedible objects, like a pen.
"Because we now know the exact site of this problem, we can work on understanding the mechanism and designing a treatment to target this symptom," he says.
Frontotemporal dementia (FTD) is a type of dementia that can affect people in their 50s and 60s, and as young as 30 years of age. There are currently no treatments for FTD.
The Neuroscience Research Australia study, published in Annals of Neurology, looked at MRI brain scans of 18 people with FTD as well as post-mortem brain tissue of a further 12 people with the disease.
"In all 30 people, we found shrinkage in the back section of the hypothalamus, the brain region that is critical for regulating our behaviour in relation to food," says Dr Piguet.
"We found that the more pronounced their eating problem, the more severe the shrinkage in the back section of the hypothalamus," he says.
Dr Piguet also found that people with particularly severe shrinkage in this region also tended to have unusual deposits of a type of protein in their brains called TDP-43.
"This suggests to us that someone with FTD who has severe eating problems is likely to have this type of abnormal protein in their brain. This will help us better diagnose the type of FTD a patient has, as well as hopefully design a treatment.
"At the moment, there are no real treatments for FTD. So if we could come up with something that alleviates this symptom, then that would really be something."