It’s not just a lack of grocery stores that’s making us fat. It’s an overabundance of fast food.
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.
In addition to being low on grocery stores, food swamps are also crammed with unhealthy food options like corner stores and fast-food places.
For a study published in November in the International Journal of Environmental Research and Public Health, researchers from the University of Connecticut’s Rudd Center for Food Policy and Obesity compared the obesity rate of U.S. counties to their ratio of fast-food restaurants and convenience stores to grocery stores and supermarkets—their level of food-swampiness, in other words.
The food swamps had about four unhealthy options for each healthy one. Food swamps were a strong predictor of obesity rates—even stronger than food deserts were. The relationship between food swamps and obesity was especially strong in areas where people lacked both their own cars and access to public transportation.
Similarly, a 2011 longitudinal study found that nearby supermarkets didn’t improve people’s diets much overall. But people—low-income men in particular—did eat more fast food when there was more fast food nearby.
Fast-food restaurants are more prevalent in areas where large numbers of people of color live. African Americans and Latinos also have higher obesity rates than whites, and this research suggests the two trends might be related.
As a potential remedy, the food-swamp study authors suggest counties could introduce zoning restrictions that would reduce the number of fast-food joints while simultaneously increasing the number of grocery stores. But they should do so carefully. Los Angeles banned new fast-food restaurants in a low-income part of the city in 2008, but the measure was considered a failure after obesity rates there continued to rise. New, healthier restaurants didn’t enter the area, and since the ordinance only targeted stand-alone restaurants, strip-mall restaurants were free to sling all the burgers and fries they wanted.
If there’s anything the food desert research shows, it’s that there’s no one silver bullet to fight health disparities. The food environment can contribute to poor health, as the grease-laden food swamps show, but changing it alone won’t immediately reverse a community’s health problems.
This article originally appeared on The Atlantic.