The term “food desert” conjures the image of a forlorn citizen, wandering through a barren landscape for miles and miles (or, by definition, for more than a mile) to reach the nearest fresh-food market. Populating food deserts with grocery stores is a favored cause among nutrition advocates, but the concept became controversial after some recent studies found the distance to the nearest grocery store doesn’t correlate with a region’s obesity rate.(Because it’s nutrition, other studies have shown the opposite. Either way, most people would agree it’s nice to be able to buy produce with relative ease, even if doing so doesn’t make you fit into your high-school jeans again.)Now, new research suggests food deserts might not be the culprit—or at least not the only one—for the high prevalence of obesity in certain areas. Instead, food swamps might be to blame.