Ahead of the Rio 2016 Olympic Games, the second Lancet Series on physical activity has been launched, providing a stark warning of the staggering human and financial cost of physical inactivity, and the limited progress that’s been made in the 4-years since the London 2012 Olympics.
By far the most publicised finding across the 4-paper series was that from Professor Ulf Ekelund and colleagues, who found that a combination of high levels of sitting and low levels of activity carry the highest risk of death. Those who sat for over eight hours but were physically active for an hour or more a day had a much lower risk of premature death than people who sat less but were also less active.
The headlines tended to take the findings a little too literally, with the Daily Mail telling readers that “adults who sit down for at least eight hours every day must do at least an hour’s daily exercise to undo all the harm.”
The research doesn’t prove that exercise undoes the damage resulting from sedentary behaviour. What it does do is highlight the multidimensional nature of physical activity and provides more evidence to help us understand how the two of the dimensions interact.
The researchers looked back at 14 studies that had already been published and at 2 unpublished studies that had relevant data and applied a standardised protocol to allow them to directly compare the data from 1,005,791 people. Including such a large number of people is a major strength of this study, but it is not without limitations – the data came from people’s estimate of their own sedentary behaviour, television watching and physical activity, which brings into question its accuracy.
The 1,005,791 people were grouped according to the time they spent sitting down each day and their weekly activity. The authors then calculated this risk of death from any cause for people in each possible combination of activity and sitting time, comparing each group to those who were most active and least sedentary.
It’s clear that increased sitting time is associated with increased risk of dying from any cause, but people with high levels of physical activity (about 60-75 minutes of moderate intensity activity a day) seem to have no increased risk of death, even if they sit for more than 8-hours a day – this is where the media got their headlines from.
It’s also worth noting that within each category of sitting time, those with higher levels of physical activity had a lower risk of death. So, whilst the optimum lifestyle would include both high levels of physical activity and as little sitting time as possible, any improvement to either dimension is likely to benefit your health.
It’s time for the world to get serious about optimising physical activity. While there has been progress in terms of policy since 2012 – in 2015, over 90% of countries had a physical activity policy – this hasn’t been translated into increased levels of physical activity, which remain low. Inactive lifestyles are condemning too many people to preventable diseases and an early death (physical inactivity is associated with more than 5 million deaths per year), not to mention the staggering INT$67.5 billion economic cost of physical inactivity worldwide.
We need to act now and deliver effective solutions at scale.
Many strategies to improve physical activity compel or prescribe and the lack of personalisation has failed to deliver successful behaviour change, in the context of individual disease risk or management. We know that physical activity is a behavioural medicine and free-living physical activity is most powerful when it’s personalised. If you want to learn more about the power of personalised data, I devoted a whole blog to it that you can read here.