Benefits of daily exercise are comparable to giving up smoking

Exercising for just 15 minutes a day can increase your life expectancy by three years compared with doing little or no exercise, according to a major study of more than 400,000 people.

The benefits of physical activity are well-documented, and the UK government recommends that adults get at least two and half hours of exercise per week. In the latest study, scientists wanted to examine whether smaller amounts of exercise could also confer health benefits.

The researchers collected data on how much exercise was undertaken over the course of eight years by more than 400,000 people in Taiwan. By categorising the participants into bands of overall activity ranging from "inactive" to "very high", they could directly compare health outcomes based on exercise levels.

Those who exercised for an average of 92 minutes per week had a 14% overall reduced risk of mortality and a 10% reduced risk of cancer compared with people in the "inactive" group. Every additional 15 minutes of exercise above and beyond the minimum amount further reduced mortality risks by 4% and risks of death from cancers by 1%.

"These benefits were applicable to all age groups and both sexes, and to those with cardiovascular disease risks," wrote the researchers in the Lancet. "Individuals who were inactive had a 17% increased risk of mortality compared with individuals in the low-volume group."

Dr Chi-Pang Wen of the National Health Research Institutes in Taiwan and Dr Jackson Pui Man Wai of the National Taiwan Sport University, who led the study, said that if inactive individuals in Taiwan were to engage in low-volume daily exercise, "one in six all-cause deaths could be postponed – mortality reductions of similar magnitude have been estimated for a successful tobacco control programme in the general population."

They added: "If the minimum amount of exercise we suggest is adhered to, mortality from heart disease, diabetes, and cancer could be reduced. This low volume of physical activity could play a central part in the global war against non-communicable diseases, reducing medical costs and health disparities."

Professor Neville Owen, head of the behavioural epidemiology laboratory at Baker IDI Heart and Diabetes Institute in Melbourne said the findings were "intriguing" but that physical activity for leisure was a rare commodity in many adult populations. In Australia, the USA and Canada, he said, leisure-time physical activity drops off rapidly from early middle age and is simply not on the agenda for a large proportion of the population.

"In these chronically inactive populations, much of the problems that we are seeing can be attributed to people being stuck for long periods of time in front of screens for work and entertainment, and stuck in automobiles to get to and from work," said Owen.

"Thus, there is very little functional physical activity in people's lives, and many adults will sit for 10 or 12 hours a day. The real action is in promoting physically active transport and a range of initiatives that will help people to reduce the vast amounts of time that they spend sitting."