Low-income urban neighborhoods or isolated rural parts of the country are often deemed food deserts — areas that have little to no fresh, healthy food sources. In food deserts, supermarkets are few and far between, and the only options within several miles are delis packed with junk food or fast food restaurants.

Perhaps surprisingly, a huge chunk of Americans (up to some 2.3 million people) live in food deserts, as shown by this U.S. Department of Agriculture (USDA) map. Lack of access to healthy, fresh foods like fruits and vegetables contributes to the obesity epidemic, diabetes, and heart disease across the country — three of largest burdens on the health care system. So what’s the best way to fight food deserts and their health consequences?

According to a recent study conducted by the nonprofit RAND Corporation, opening a supermarket in a food desert could lead to improvements in diet, but not necessarily because people end up using the supermarket.

“We found multiple positive changes following the opening of the supermarket in a former food desert, yet the changes in diet were not related to use of the supermarket,” said Tamara Dubowitz, lead author of the study and a senior policy researcher at RAND, in the press release. “Our study is the first to provide evidence of dietary improvements and wellbeing changes in response to a new market. This supports federal efforts to help open grocery stores in food deserts, but also provides a very strong case for continued evaluation of this policy to understand exactly what the mechanisms might be.”

The researchers analyzed a neighborhood in Pittsburgh that saw a supermarket open for the first time in decades. The 1,372 residents who enrolled in the study (who were mainly African-American women) reported eating fewer calories and smaller amounts of sugar, and were happier with their neighborhood after the supermarket opened — possibly due to the perception that they had access to healthier foods.

But while the participants reported a reduced intake of solid fats, alcohol, and sugars, the results still remain murky. Overall obesity rates didn’t decrease during the study period, and in fact, the consumption of fruits and vegetables declined. It was merely the perceived access to healthy foods that made a difference, offering people a greater sense of choice in deciding what to eat. The researchers also noted previous studies that examined the impact of a new supermarket in a food desert had discovered they didn’t do much to change the dietary habits of residents, particularly when it came to obesity and intake of fruits and vegetables.

“After the opening of the supermarket, we saw improvements in diet, perceived access to healthy foods, and satisfaction with their neighborhood as a place to live,” Dubowitz said. “However, the only outcome that was directly related to use of the store was perceived access to healthy foods. Those residents who reported the most improved access to healthy foods also used the store more frequently.”

While the study may not answer any questions about how to fight food deserts and the obesity epidemic, the researchers plan to further investigate how perceived access to fresh, healthy food could benefit neighborhoods in the long run. “If we are going to push the needle forward to improve population health," Dubowitz said, "we may need to explore how investing in neighborhoods might ultimately translate into improvements in the health and well-being of residents."

Source: Dubowitz T et al. Health Affairs. 2015.