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Active commuting lowers BMI and body fat

Studies have found cycling at 3 hr/week and walking 2 hr/week lowers mortality by 28% and 39% respectively from all cause mortality.
Studies have found cycling at 3 hr/week and walking 2 hr/week lowers mortality by 28% and 39% respectively from all cause mortality. GettyImages/Darrin Klimek

Walking, biking or taking public transportation to work lower risk of obesity

A new study published in BMJ find men and women who commute by public or active transportation is linked with significantly lower BMI and body fat composition.
A new study published in BMJ find men and women who commute by public or active transportation is linked with significantly lower BMI and body fat composition.GettyImages/.Markus Bernhard

The beneficial effects of physical activity on obesity and related health outcomes are generally well understood. In high and middle income countries however, lifestyles have become increasingly sedentary, and physical inactivity has become the fourth leading risk factor for premature mortality. Declining rates of functional active travel have contributed to this population-level decrease in physical activity, and ecological evidence suggests that rising levels of obesity are more pronounced in settings with greater declines in active travel.

Active commuting to work has been strongly recommended by the UK National Institute for Health and Care Excellence (NICE) as a feasible way of incorporating greater levels of physical activity into daily life.

In this new study researchers, from the London School of Hygiene & Tropical Medicine and UCL set out to determine if promotion of active modes of travel is an effective strategy for obesity prevention by evaluating whether active commuting (walking or cycling for all or part of the journey to work) is independently associated with two known markers of obesity; body mass (BMI) and percentage of body fat.

The team evaluated 7.534 BMI measurements and 7,424 percentage body fat measurements from men and women who had taken part in the Understanding Society, the United Kingdom Household Longitudinal Study (UKHLS), a large, nationally representative dataset.

A total of 76% of men and 72% of women commuted to work by private motorized transport, 10% of men and 11% of women reporting using public transport, while 14% of men walked or cycled to work compared with 17% of women. Overall BMI score for men was 28 and 27 for women.

Generally, a BMI of 18.5 to 24.9 indicates optimal weight, a BMI lower than 18.5 suggests the person is underweight, a number above 25 may indicate the person is overweight, and a number above 30 suggests the person is obese.

The results revealed those who traveled to work by public and active modes significantly and independently predicted lower BMI and healthier body composition in both men and women compared to private transportation.

Men who commuted via public or active modes had BMI scores around 1 point lower than those who used private transport, equating to a difference in weight of 3kg (almost half a stone) for the average man.

Women who commuted via public or active transport had BMI scores around 0.7 points lower than their private transport using counterparts, equating to a difference in weight of 2.5kg (5.5lb) for the average woman.

Results for percentage body fat were similar in size and significance. And the associations remained after adjusting for several potentially confounding factors, such as age, presence of a limiting illness or disability, monthly income, social class, level of physical activity in the workplace and diet.

The researchers commented that the differences are "larger than those seen in the majority of individually focused diet and physical activity interventions to prevent overweight and obesity."
The researchers point out their study was large, no firm conclusions can be drawn about direct cause and effect. However, they say the use of public transport and walking and cycling in the journey to and from work "should be considered as part of strategies to reduce the burden of obesity and related health conditions."

The research team writes “Further research using longitudinal data with high quality exposure and outcome measures is required in order to confirm the direction of causality in the association between active commuting and body weight.”

In an accompanying editorial, researchers from Imperial College London say there is an increasing interest in persuading the public to drive less and to walk and cycle more to achieve health, transport, and environmental policy objectives. Unfortunately, they point out that active commuting has declined steadily in most high income countries since the mid-20th century as car ownership has grown.

They say, given the political sensitivity around policy measures that discourage use of cars, "it is crucial that the public health community, including healthcare professionals, provide strong and consistent messages to politicians and the public which frame these measures as positive public health actions."

This study is published in the British Medical Journal (BMJ)

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