Increasing the availability of public transit systems is one among a number of modifications to the built environment that offers opportunities for increasing physical activity and reducing the prevalence of obesity and its associated problems. In a study published in the August issue of the American Journal of Preventive Medicine, researchers from the University of Pennsylvania, Drexel University and the RAND Corporation found that construction of a light-rail system (LRT) resulted in increased physical activity (walking) and subsequent weight loss by people served by the LRT. These findings suggest that improving neighborhood environments and increasing the public’s use of LRT systems could improve health outcomes and potentially impact millions of individuals.

Public policy implications of the study are significant. “The built environment can constrain or facilitate physical activity. Understanding ways to encourage greater use of local environments for physical activity offers some hope for reducing the growth in the prevalence of obesity,” commented lead investigator John M. MacDonald, PhD, University of Pennsylvania.

“Given that perceptions of neighborhood environments are independently associated with improved health outcomes, and that individuals who choose to use LRT obtain some relative weight reduction, it would be prudent to encourage public policies that improve the safety and attractiveness of pedestrian environments that link home, work and transit stops to increase use of public transit for commuting to work.

Public policy investments in transit should consider potential increases in physical activity as part of the broader set of cost–benefit calculations of transit systems. Land- use planning and travel choice have a clear impact on health outcomes. Public transit systems can generate positive health impacts by encouraging greater numbers of users to walk to station stops and maintain more physically active lives. An added benefit of public policy investments in LRT, on top of the general transportation benefits accrued, is the potential reductions in obesity in the population.”

Using two surveys, one collecting data prior to the completion of an LRT in Charlotte, North Carolina, the second after completion, investigators found that using light rail for commuting was associated with reductions in body mass index (BMI) over time. Specifically, LRT reduced BMI by an average of 1.18 kg/m2 compared to non-LRT users in the same area over a 12-18 month follow-up period. This is equivalent to a relative weight loss of 6.45 lbs for a person who is 5’5. LRT users were also 81% less likely to become obese over time.

Survey questions assessed level of physical activity, BMI, perception of the neighborhood environment, public transit use before and after LRT construction, any plans to use LRT when available, and actual LRT usage.

There are currently 32 LRT systems operating in major U.S. metropolitan areas, generating over 200 million passenger trips a year.

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The article is “The Effect of Light Rail Transit on Body Mass Index and Physical Activity” by John M. MacDonald, PhD, Robert J. Stokes, PhD, Deborah A. Cohen, MD, MPH, Aaron Kofner, MS, and Greg K. Ridgeway, PhD. It appears in the American Journal of Preventive Medicine, Volume 39, Issue 2 (August 2010) published by Elsevier.

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