There’s a new study out, based on research from Taiwan, that shows that exercising for just 15 minutes a day (about 1.5 hours a week) is associated with a 14 per cent reduced risk of death over a the course of the study compared with being sedentary . This study is wildly being reported as evidence that even low levels of activity (lower than generally recommended) can delay death. Much that I would like this to be so, from a scientific standpoint, this is a conclusion too far, I think.
The reason for this is that the study in question is what is known as ‘epidemiological’ in nature, which means it is assessing associations between things (in this case, exercise habits and risk of death over time). Associations, though, do not prove causality. We don’t know from these sort of studies if exercise is having a direct positive impact on health. It might, for example, be the other way round. Maybe individuals who are healthier are more inclined to exercise. Maybe being sedentary is a sign of sickness. Basically, we just don’t know. All we know is that even low levels of activity is associated with reduced risk of death.
That said, in my heart (more than my head) I believe that even relatively low levels of activity is indeed likely to benefit health and stave off death. I see activity and exercise as a pillar of health. Long-term studies which randomise people exercise or non-exercise groups and then follow them until death (to see if exercise actually reduces death risk) do not exist. However, we do have shorter-term studies that show improvements in terms of disease markers. These are changes we would expect to translate into reduce risk of disease (and perhaps death) in time.
Also, with exercise, I think there is a ‘law of diminishing returns’. Let’s say you exercise for an hour each day. How much more is to be gained from exercising for say, an hour and 15 minutes? The incremental benefit is likely to be small in comparison to the benefit had from exercising for an hour.
However, if we go from no activity (sedentary behaviour) to 15 minutes of daily exercise, the relative benefit is likely to be huge in comparison. This is one of the reasons I encourage normally sedentary individuals to do something.
In my last book – Waist Disposal – I included a brief, home-based exercise session made up of mix of resistance exercises (like press-ups, sit-ups and squats) and more aerobic exercise (running on the spot). The session is designed to be 12 minutes long. Compared to doing nothing, this brief session can do wonders for improving strength and physique, and I believe it likely impacts positively on health too. This sort of regime is unlikely to allow us to qualify for next year’s Olympics, but I believe it’s impact on health and wellbeing can be profound.
Tack this sort of regime on to recreational walking and perhaps some stretching, and I believe our exercise ‘needs’ will be largely met.
This new study from Taiwan tells us very little about the purported benefits of exercise, and I think its findings have been overstated. However, I utterly support its message: devoting even small amounts of time to activity and exercise is much, much better than doing nothing.
1. Chi Pang Wen, et al. Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study. The Lancet, Early Online Publication, 16 August 2011