The scientists have found that physical activity helps stimulate blood circulation in areas at risk in the front of the brain, reports Daily Express.
Dementia is a growing problem worldwide, due to an ageing population and it has significant human and economic costs.
While talking about the research, study's lead author Alice Hollamby said, "We understand that living with dementia poses many challenges to individuals and their families and the idea of improving their physical fitness may seem like an unachievable target."
She added, "However, we encourage increased physical fitness in any way - even what may seem like minor steps. Just helping out around the house or in the garden, taking a short walk or swim, or lifting things from a seated position could play a big part in slowing the progression."
Meanwhile, study co-author Dr Eddy J Davelaar, noted, "We all know we should embrace a healthy lifestyle to strengthen our physical and mental wellbeing. However, this is not to say that when one develops dementia, all hope is lost."
"Our findings suggest that prior levels of physical activity did not influence the association between cognitive performance and physical fitness. This means it is never too late to start," explained Davelaar.
The team stressed that more research is still needed into the link between physical and mental fitness.
Evidence has long suggested that physical fitness may help to prevent dementia, but the latest study further implies it could ward off further memory loss in the 850,000 Britons who are suffering from the condition.
The study's senior author, Dr Dorina Cadar, from UCL, said: "Dementia is such a cruel disease which causes confusion and disorientation to the sufferer and enormous distress to their families and loved ones. Our study has helped to identify risk factors that could modify the rate of cognitive deterioration and disease progression."
The findings follow evidence that older adults with dementia are better able to count backwards from 50 or name the months of the year in reverse while walking for 10 minutes.
The study was published in journal Frontiers in Public Health. (ANI)