PUBLIC HEALTH:

Study links sprawl, obesity

Car-loving Charlotte, N.C., home to strip malls and suburban sprawl, did everything right when putting in place its new light-rail transit system called the Lynx in 2007. The result: a ridership that doubled predictions, and an unexpected public health study that may be the first in proving that the built environment causes obesity.

Riding the rails can leave users an average of 6.5 pounds lighter than others, and 81 percent less likely to become obese over time, according to the study, published in the American Journal of Preventive Medicine.

"If you lose about 5 to 10 percent of body weight, that might be enough to prevent conditions such as Type 2 diabetes," said Jean Gutierrez, visiting assistant professor of exercise science at George Washington University, and an exercise expert unconnected to the study.

Before this study, it was difficult to say for certain whether the features of the built environment, such as sprawl and miles of roadway, are directly responsible for obesity and related illness such as cardiovascular diseases and diabetes. Research can get confusing since a complex mix of choices can lead to weight gain, including people's attitudes.

It is possible that people with an appetite for health foods, biking and exercise naturally gravitate toward cities that feature conveniences such as light rail and bike lanes; and people who want enjoy the wide expanses of suburbia search out locations that can support their lifestyle.

In Charlotte, researchers managed to avoid most of these confounding factors by surveying a group of residents who had lived in the area before the system had ever been talked about. Presumably, all other lifestyle choices that can lead to weight loss or gain, including attitudes and food habits, would remain independent of the arrival of the Lynx. They talked to the residents before and after the rail line was built and took down their self-reported body mass index values.

Their findings supported what had long been suspected -- light-rail transport could lead to more walking by an average of 1.2 miles a day. The 1995 Dietary Guidelines for Americans recommends a minimum of 30 minutes of moderate-intensity physical activity per day, a number that could be met by having a public transport system, said Gutierrez.

This study is a good first step to proving that our built environment causes obesity, Gutierrez said. But it needs to be backed up by better measurements -- perhaps pedometer steps -- and by randomly assigning people to different modes of transportation, including the Lynx, as a way to compare between transport choices, she said. Such studies may be difficult since public health impact assessments are not a regular part of rail building.

In its first year, at the peak of the gasoline price rise, Charlotte's Lynx saw about 18,100 riders, which was double the number expected, said Robert Stokes, researcher at University of Pennsylvania's department of culture and communication, and co-author of the study. The numbers have maintained. The city did all the right things when putting in place the light-rail system, Stokes said. It chose to put the line close to places where people lived, which increases ridership, according to studies. The corridor stretches 9.6 miles and has 15 stops.

Charlotte also changed its zoning laws to allow development closer to rail stations, and a greater concentration of units. It was a policy change, said Stokes. Since World War II, zoning laws in the nation promoted a separation between commercial, residential and recreational land use in the built environment, leading to more sedentary lifestyles. About half of all Americans do not get enough physical activity to promote health, and about 25 percent do not get any exercise at all, according to the Centers for Disease Control and Prevention's 2007 statistics.

The situation is worse in Charlotte because, out of 41 metros in the United States, the city ranks 40th in population density, increasing the risk of obesity.

Given this situation, public policy that plans the built environment needs to account for public health costs surrounding obesity, said Stokes.

"The Charlotte light-rail system is no different from large infrastructure projects," Stokes said. "In the environmental impact assessment, there is no catagory for public health impact. ... If you are going to invest in transit systems, you should not just include pollution abatement, noise, vehicle miles driven, but also potential health care costs savings."

In an earlier report even before the system was built, the same researchers estimated that the Charlotte LRT system could save $903,000 in health care costs in the first year, assuming a ridership of 9,100 people. The study found that by 2015, the savings could rise to $12.6 million. While average operating costs for LRTs is about $778.3 million, incorporating rail into the built environment together with other changes such as pedestrian friendly streets, would maximize the public health benefits, according to the study.

"The federal government should take this into account," Stokes said. "The president just announced a transit system plan, a lot of it goes to roads." He called for public health to be included as one of the drivers for public policy.

President Obama called Monday for Congress to approve a $50 billion plan that will rebuild the nation's infrastructure, including 150,000 miles of roads, 4,000 miles of rail tracks, and 150 miles of runways.