A study by Monash University has drawn a sharp line between where fat is stored in the body and the risk of dementia in older Australians, particularly men. The findings, based on data from more than 17,000 participants aged 65 to 98, indicate that belly fat may increase dementia risk, while higher lean and overall fat mass in the body could actually offer some cognitive protection.
Published in the Journal of the American Alzheimer’s Association, the research comes from the ASPREE (ASPirin in Reducing Events in the Elderly) study and was led by a team from Monash’s School of Public Health and Preventive Medicine. Professor Joanne Ryan, senior author and head of the Biological Neuropsychiatry and Dementia unit at the university, says the location and type of fat appear to matter more than previously assumed.
“Higher lean body mass and fat body mass in later life may be associated with better cognition, while abdominal fat could be a risk factor, particularly in men,” the study found.
The researchers discovered that those in the higher quartiles of lean or fat mass showed a 15 to 38 per cent lower risk of developing dementia compared to those with lower mass. But when fat is concentrated in the abdominal region, especially in males, the protective effects may be lost, or even reversed.
This nuance challenges long-standing assumptions around weight and ageing. While excess body weight during midlife has long been linked to poorer health outcomes such as diabetes and cardiovascular disease, both known contributors to dementia risk, these new results suggest the story changes after 65.
Professor Ryan elaborated: “Our findings suggest that increased body weight in older age may confer protective effects on brain ageing, regardless of body composition. However, abdominal adiposity may still be a risk factor for cognitive impairment in older individuals, particularly in men.”
She added that these results point to a more complex relationship between body composition and brain health than previously thought. It’s not simply about how much body fat one has, but where that fat is located and how it’s balanced against lean mass.
The study doesn’t imply that weight gain should be encouraged in older adults, but rather that health strategies may need to be more targeted, focusing less on weight alone and more on body composition and fat distribution.
“Lifestyle strategies, such as a healthy diet and regular exercise, likely play a role in protecting brain health for older individuals,” Professor Ryan said.
These strategies may include resistance training to preserve or increase lean muscle mass, and moderate cardiovascular activity to reduce central fat. More research is needed to determine the precise biological mechanisms at play, but inflammation, insulin resistance, and hormonal factors may be part of the story.
The ASPREE study, which originally aimed to assess the impact of low-dose aspirin on healthy ageing, has since become a valuable trove of information on the later stages of life, covering everything from cardiovascular events to mental decline. This latest finding adds another layer: the idea that not all fat is created equal.
With Australia’s ageing population expected to swell in coming decades, and dementia already one of the leading causes of death in the country, findings like these could help sharpen public health messaging around prevention.
As weight loss messaging for midlife adults often dominates headlines, this study reminds us that the science is more layered when it comes to older populations. For older Australians—and particularly men, what’s around the waist may deserve a closer look.
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