A study of about 500 people in Charlotte, N.C., before and after the city completed a light-rail system found that those who used the system to commute were 81 percent less likely to become obese. They also reduced their Body Mass Index over a period of 12 to 18 months by an average of 1.18 points, which is the equivalent of 6.45 pounds for a person 5-foot-5, the study published in the August issue of the American Journal of Preventive Medicine found.
“People in the suburbs drive everywhere, while people in the city walk and use mass transit — the latter burning more calories,” says Dr. Whelan. “When you add up calories expended on a daily basis by walking, it can really add up.”
But Stier worries the study’s take-home message is too simplistic. “I don’t love the urban planning message,” he says. “If you live in an area without mass transit, that doesn’t mean you’re doomed to a life of obesity; it just means you need to take into account that you’re driving more and walking less, and you should be more active. I don’t like the idea here that to fight obesity we just need to put in a subway line, and for each new subway line we’ll reduce obesity by 1 percent.”