Regular walking can help prevent the brain from shrinking in old age, a new study suggests.
According to researchers at the University of Pittsburgh, an energetic stroll three times a week could increase the size of the hippocampus, the part of the brain that stores memories.
As people age, some brain shrinkage is normal. However, walkers aged between 55 and 80 were found to have grey matter than was two inches larger in key areas.
Dr Kirk Erickson, who unveiled the study's findings at the American Association for the Advancement of Science's annual conference in Chicago last week, said the growth is the equivalent of taking two years off the age of a person's brain.
He explained: "You don’t need highly vigorous physical activity to see these effects. This may sound like it is a modest amount, but it’s like reversing the age clock by a couple of years.
He added that too many people lead sedentary lives, but fail to realise that the detrimental effect it could be having on their health.
As well as walking, mental exercise, such as solving puzzles, can be beneficial to the brain and has also been linked to a slowdown in shrinkage.
The study involved 120 men and women walking for an average of one hour and 20 minutes a week for a year. Each was required to record the amount of time they spent walking before their brains were scanned.
Because the hippocampus is the area most affected by Alzheimer's disease, the team feel regular exercise could help lower a person's chances of being diagnosed with dementia.
Earlier this month, research from the University of Maryland found a link between people with impaired hearing, brain shrinkage and dementia.
An estimated 820,000 people are currently living in the UK with some form of dementia and the figure is likely to rise above one million by 2021.