So why do people not do enough exercise? “No time.” “Not my thing.” We have all heard the reasons. This is why active travel (walking or cycling) is such a good way to get exercise. It often saves you time and in addition it saves you money. And it helps the environment.
But does exercise in the form of active travel actually improve your health? We know from surveys that active travelers are healthier. But if you start commuting by active travel does your health improve? There have been a few small experimental studies that indicate that it does. But now we have some impressive evidence from two large scale surveys. Both studies looked at body mass index (BMI, kg/m2) a measure of how fat you are and a good index of general health and fitness.
The British Household Panel Survey ran from 1991 to 2009 and each year asked the 18,000 participants about how they travelled to work. From 2004-2007 they were also asked their height and weight, enabling BMI to be calculated. Over this period complete data was obtained from 4056 people of whom 109 switched from car travel to active travel (walking or cycling) and 156 switched the other way. For those switching to active travel, BMI fell by 0.32, equivalent to about a 1 kg reduction in weight. This may not sound much but the change occurred over about 1 year, not very long. And across the population, a reduction of BMI of this extent would be hugely helpful to an overstretched heal th service. Most impressive of all, the fall in BMI was greater the longer your commute (See chart above).
The few subjects who changed from the car to a greater than 30 min commute by walking or cyclinig had a BMI reduction of 2.25, equivalent to a 6kg (14lb – a stone!) fall in weight.
The British Household Panel survey also includes every year a questionnaire on psychological wellbeing (GHQ-12, questions on self-worth, ability to cope etc). Switching from car to active commute was associated with a significant improvement in wellbeing.
Data from the UK Biobank study shows a similar trend. The Biobank is a large database of 40-69 year-olds that includes BMI and mode of travel to work. Of the 500,000 participants, 20,000 have now had repeat measurements made, at an average 4.4 years interval. Of these, 5861 had data on commuting travel and all other relevant measures. The numbers switching from car travel to active transport or vice versa were too small for separate analysis (about 40 each way). So the analysis here is for a switch from car travel to either public transport or active transport and vice versa. Those abandoning their cars showed an improved BMI, on average 0.30 lower. In contrast those switching to a car commute put on weight, increasing BMI by 0.32. So changing travel mode triggered about a 1kg change in weight, down for those going to public or active travel, up for those switching to cars. See chart above).
These studies are important because they look at trends across large populations, so the statistical reliability is good. Lots of other data was also available about the survey participants so the analyses were able to allow for any possible bias due to differences in occupational status, working hours, household income, health status and a host of other factors that might influence the results. The Biobank study only analysed combined public and active travel. But we know from other studies that health indices in people using active transport are better than those using public transport, so the trend for both is very likely to include a similar or better trend for those switching to cycling and walking.
As a cyclist it would be even more interesting if these studies had contained separate data on cycling. Living in London where commute distances tend to be long, cycling is the time efficient option. Unfortunately not many people cycle to work. In order to find people who start cycling to work we would need an even bigger survey. The Biobank survey is ongoing and may eventually deliver enough data. But the message is clear. Active travel to work is good for your health and wellbeing.
Adam Martin, Yevgeniy Goryakin, Marc Suhrcke. (2104) Does active commuting improve psychological wellbeing? Longitudinal evidence from eighteen waves of the British Household Panel Survey. Preventive Medicine 69 296–303
Flint, ES; Cummins, SCJ. (2016) Is active commuting associated with obesity in mid-life? Cross-sectional, observational evidence from UK Biobank. The Lancet Diabetes & Endocrinology 4, 420-435
Ellen Flint, Elizabeth Webb, Steven Cummins (2016) Change in commute mode and body-mass index: prospective, longitudinal evidence from UK Biobank. Lancet Public Health October 28, 2016
Martin A, Panter J, Suhrcke M, et al. (2015) Impact of changes in mode of travel to work on changes in body mass index: evidence from the British Household Panel Survey. J Epidemiol Community Health 69:753–761.