It takes only 30 minutes a day but could cut your risk of falling victim to up to two dozen illnesses, including dementia and cancer.
Taking the time for a brisk daily walk could also have other major health benefits by slowing down the rate at which our bodies deteriorate with age.
Researchers made the dramatic claims after examining 40 previous studies over the last four years.
They found that being fit and active ranks alongside not smoking as the most powerful choice we can make to stay healthy.
And its benefits are universal, helping men and women in all age groups. The study classed regular moderate physical activity as 150 minutes a week, such as 30 minutes of brisk walking or cycling, five days a week.
This, it said, is associated with a decreased risk of heart disease and stroke.
There is growing evidence that this daily bout of exercise could also decrease the risk of dementia in older age.
Other benefits could include a reduced risk of a list of other conditions such as osteoporosis, type 2 diabetes, depression, obesity and high blood pressure.
Research has also found that a simple half-hour a day of exercise was associated with a reduction in the risk of cancer.
If you can step it up to an hour a day, then the gains rise as well, with the incidence of cancer falling by even more.
Evidence, however, is mixed when it comes to specific cancers. Research has shown a strong relationship between increased physical activity and reduced colon cancer in both sexes.
And men who are more active at work, rather than just sitting at a desk, have lower rates of prostate cancer, according to the report in the International Journal of Clinical Practice. Other cancer studies have shown that physical activity after diagnosis can aid recovery and improve chances of survival.
Physiotherapist Leslie Alford, a lecturer at the University of East Anglia, said: ‘It appears our bodies have evolved to function optimally on a certain level of physical activity that many of us simply do not achieve in our modern, sedentary lifestyles.
‘What is clear from the research is that men and women of all ages should be encouraged to be more physically active for the sake of their long-term health.’
He added that other factors can boost the effects of a daily walk, such as not smoking, eating healthily and not being overweight.