If you’re over 40, and spend more time on the couch than not, have you ever wondered what difference it would make to your life if you went for a walk?

Australian researchers have asked and answered this question with encouraging results.

In a predictive modelling study, they have estimated “the impact of different levels of increased physical activity on life expectancy”.

On average, the researchers found, taking a single one-hour walk could add an extra three hours to your life.

Looking specifically at slackers, if you’re among the least active people, the benefit doubles. That is, a single one-hour walk could add an extra six hours to your life.

How they worked this out

The study included researchers from the Public Health & Economics Modelling Group, Griffith University School of Medicine and Dentistry, and the University of Sydney School of Public Health.

They based their model on physical activity risk estimates derived from US activity tracker data.

This included the 2003-06 National Health and Nutritional Examination Survey for people aged at least 40 – and population data from the US Census Bureau and deaths recorded in 2017 from the National Centre for Health Statistics.

The modelling came up with some fascinating numbers.

The total physical activity of the most active 25 per cent of Americans over the age of 40 “was equivalent to 160 minutes of normal-paced walking at 4.8 kilometres per hour, every day”.

Based on this, the researchers estimated that if all the over-40s in the US matched this level of physical activity every day, their average lifespan would increase by just over five years.

This would boost life expectancy at birth to nearly 84 years from 78.6 years.

Good and bad news for slackers

It’s not news that doing little to no exercise is associated with a higher risk of heart disease and stroke, as well as premature death.

What hasn’t been clear is the “extent to which low physical activity levels shorten lifespan in specific groups of people or countries”.

For an extra challenge, try walking on a rocky path. It’s good for your balance. Photo: Getty

By calculating the beneficial effect on life expectancy for people who do little exercise, the researchers got an idea of how early these are dying.

They found that “if the least physically active 25 per cent of the population matched the levels of the most physically active 25 per cent, they would need to clock up an extra 111 minutes of walking at 4.8 kilometres per hour, every day (or equivalent effort)”.

That’s the better part of two hours a day – a challenge for sure, with a target that you would need to work up to.

But the benefits are astonishing: The estimates suggest these people could increase their life expectancy by nearly 11 years.

This suggests that without making that effort, they could be dying 11 years earlier than they need to.

Overall, “the greatest gain in life for every hour walked was seen among the least physically active, among whom each extra hour of walking could add 376 minutes to their life expectancy – equivalent to around six hours”.

Gains to life expectancy decreased as physical activity rose.

“Our findings suggest that [physical activity] provides substantially larger health benefits than previously thought, which is due to the use of more precise means of measuring [it],” they write.

“The greatest gain in lifetime per hour of walking was seen for individuals in the lowest activity quartile where an hour’s walk could add an impressive six hours to life.”

This is an observational study and, as such, can’t establish cause and effect, and the researchers acknowledge various imitations to their findings.