Here is another reason to get people out of their cars: They lose weight fast. A study in the UK checked the body mass index of 7534 people and the percentage of body fat for 7424 people and found that "commuting by public or active transport modes was significantly and independently predictive of lower BMI for both men and women." Men who take transit are about seven pounds lighter; women, about 5.5 pounds lighter.

The most interesting takeaway from the study, done by Research Fellow Ellen Flint and published in the British Medical Journal, was that the positive effect of active transportation wasn't limited to those who walk or ride bikes (There's lots of evidence for that) but also those who take public transit. Evidently all those walks to the bus stop and climbing those stairs through the subway stations add up to significant physical exercise.

A key finding from this study is that the effects observed for public transport were very similar in size and significance to those for walking or cycling to work.

© UrbanToronto/ the endless Spadina Station tunnel. No wonder people lose weight.

This is significant; all of the investment being made in transit in cities across North America is usually justified as a way of getting cars off the road; now it appears that there is an additional benefit- the cost of building and operating transit can be offset by a reduction in health costs. Flint concludes:

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.

More in the Telegraph.

© John Pulcher Keynote deck

This builds on earlier work by Rutgers University Professor Jon Pucher, who found that obesity falls sharply with increased walking, cycling and transit use. See more in TreeHugger here.

Related on TreeHugger.com:

• New study confirms: the suburbs make you fat
• Urban Planners Make You Fat
• Cul de Sacs and 11 Other Unexpected Things That Are Making You Fat