Is your car journey making you fat?
Middle aged adults who get the bus to work have less body fat and weigh less than those who commute by car, according to a new study.
And those who cycle or walk to work are leaner still, with male cyclists weighing five kilos less than driving commuters.
Those who use public transport for their daily commute have a lower body mass index (BMI) and percentage of body fat compared to car commuters.
The British study, the largest yet on the health benefits of active transport, looked at data from over 150,000 Britons aged between 40 and 69.
The strongest differences in body weight were seen when comparing cyclist commuters with those who used a car to get to work.
For the average man in the sample, the data gathered showed cyclists were weighed 5kg - 11lbs - less than those who drove.
For the average woman, this weight difference was 4.4kg - 9.7lbs.
After cycling, walking to work showed the next greatest reduction in BMI and percentage body fat, when compared with car users.
For both cycling and walking, greater travelling distances were associated with greater reductions in BMI and percentage body fat.
Commuters who only used public transport also had a lower BMI compared to car-users, as did commuters who combined public transport with other active methods.
The link between active commuting and BMI was independent of other factors such as income, area deprivation, education, smoking and overall health.
In England and Wales, 23.7 million individuals regularly commute to work, two thirds - 67 per cent - by car.
In the study sample, 64 per cent of men and 61 per cent of women commuted by car.
Only four per cent of men and two per cent of women only cycled or mixed cycling and walking.
Previous studies that have looked at active commuting have tended to combine cycling and walking with other methods of active commuting, perhaps understating the positive effects of cycling.
With the majority of people in mid-life commuting by car, the authors of the study said that obesity reduction could be achieved by encouraging and incentivising a more active lifestyle.
Lecturer in Population Health Dr Ellen Flint of the London School of Hygiene & Tropical Medicine said encouraging active commuting could be “important” for obesity prevention.
She said: “Even when accounting for demographic and socioeconomic factors, public transport, walking and cycling are associated with reductions in body mass compared with commuting by car.
“Many people live too far from their workplace for walking or cycling to be feasible, but even the incidental physical activity involved in public transport can have an important effect.
“Physical inactivity is one of the leading causes of ill-health and premature mortality.
“In England, two thirds of adults do not meet recommended levels of physical activity.
“Encouraging public transport and active commuting could be an important part of the global policy response to population-level obesity prevention.”
The study was published in science journal The Lancet: Diabetes & Endocrinology.
Commenting on the findings Professor Dr Lars Bo Andersen of the Sogndal and Fjordane University College, Norway, said: “The finding of a positive effect from active commuting is important, because commuting to work is an everyday activity that lots of working people need to do.
“Many people are not attracted to recreational sports or other leisure time physical activities, which are proven to benefit health, and active transport might therefore be an important and easy choice to increase physical activity and the proportion of people achieving recommended levels of physical activity. “Physical activity during commuting has health benefits even if its intensity is moderate and the commuting does not cause high heart rate and sweating.”