But two new studies have found something unexpected. Such neighborhoods not only have more fast food restaurants and convenience stores than more affluent ones, but more grocery stores, supermarkets and full-service restaurants, too. And there is no relationship between the type of food being sold in a neighborhood and obesity among its children and adolescents.

Within a couple of miles of almost any urban neighborhood, “you can get basically any type of food,” said Roland Sturm of the RAND Corporation, lead author of one of the studies. “Maybe we should call it a food swamp rather than a desert,” he said.

Some experts say these new findings raise questions about the effectiveness of efforts to combat the obesity epidemic simply by improving access to healthy foods. Despite campaigns to get Americans to exercise more and eat healthier foods, obesity rates have not budged over the past decade, according to recently released federal data.