Greenwire: 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 …