Early results from a new study led by ANU indicate that people aged in their 60s and early 70s could lower their risk of dementia if they maintained a healthy weight by going to the gym to retain muscle mass.
Lead researcher Dr Marnie Shaw said about one in 10 Australians aged 65 years and older will get dementia.
"As our population ages, the number of people with dementia will increase, but an active lifestyle offers real opportunities for reducing dementia risk," said Dr Shaw from the ANU Research School of Electrical, Energy and Materials Engineering.
The researchers observed about 400 people aged in their 60s and early 70s from Canberra at several different stages over time.
Dr Shaw said the study was the first to show that the relationship between body mass index (BMI) and brain shrinkage changed from midlife to older age.
Research evidence has linked brain shrinkage to the onset of dementia.
"Both increasing and decreasing BMI was associated with more brain shrinkage at an older age," Dr Shaw said.
She said a weight loss during people's later years was common and often due to losing muscle mass.
"Preliminary results from our research indicate that it's important for people in later years to go to the gym to maintain a healthy weight and not lose their muscles," Dr Shaw said.
The other main risk factors for dementia include midlife obesity, physical inactivity, smoking, hypertension and depression.
ANU collaborated with the University of New South Wales on the research, which is published in the International Journal of Obesity.
This research is part of a larger study, called the 2sweet project, which is led by Associate Professor Nic Cherbuin at the ANU Research School of Population Health.