Surprisingly, people who live more than a half mile away from any food outlets are the ones who tend to be fatter. The study suggests that placing restrictions on fast food outlets may not be effective, but that initiatives to increase healthy neighborhood food options may reduce individuals' obesity risks, especially if focused on low-income neighborhoods.
"Having access to a range of food options in your neighborhood affects both your energy input and output," says Cathleen Zick, coauthor of the study and professor of family and consumer studies at the University of Utah. "A healthy grocery option may influence the food you choose to buy, while having multiple food destinations within walking distance might encourage you to walk, rather than drive, to your next meal."
In a 2008 study, Zick and colleagues found that residents were at less risk of being obese or overweight if they lived in walkable neighborhoods—those that were more densely populated, pedestrian friendly and had a range of destinations for pedestrians.
Folding food environment into the mix, their current study demonstrates how important proximity to healthy food options can be to your waist line.
The new study in Social Science and Medicine compared the body mass index (BMI) of nearly 500,000 Salt Lake County residents with food-related business addresses within their neighborhoods. Researchers found that residents were 10 percent less likely to be obese if they lived in a neighborhood with a diversity of food options, such as healthy groceries, full-service restaurants, convenience stores and fast-food restaurants, compared with residents with no food options in their neighborhoods.
The study also found that neighborhood income level plays a role in obesity. The researchers found that residents in low-income neighborhoods, defined as having an average household income in the lowest quartile of the 2000 census, were 26 percent less likely to be obese if there was one or more healthy grocery options within walking distance, compared with low-income residents without neighborhood retail food outlets.
"Food environment matters differently for poor and non-poor neighborhoods," says Zick. "A full-service grocery store means more in low-income neighborhoods where access to private transportation may be limited."
Zick adds that residents in non-low-income neighborhoods do not benefit the same from having a full-service grocery nearby. Rather, it is the presence of full-service restaurants in such neighborhoods that is associated with a lower obesity level.
"We can speculate this is because people with access to private transportation are more likely to drive to the grocery store anyway, whereas having restaurants within walking distance may encourage walking," she says. "It is residents with no nearby food options who are at greatest risk of obesity. Not only are they without healthy grocery options nearby, there are no destinations to walk to, not even fast food. They must drive."
Zick and colleagues used three sources to analyze body mass index in relationship to neighborhood characteristics such as walkability and food environment.
Using data from the 2000 census, researchers assessed walkability features of 566 census-block groups in Salt Lake County, looking at population density and the fraction of residents who walk to work. Both factors related to body mass index in the 2008 study.
They then used the 2008 Dun and Bradstreet business data directory to link local food-related business addresses with block groups via geographic coordinates.
Using height and weight data from the Utah Population Data Base at the University of Utah, they calculated the body mass indices of 453,927 Salt Lake County residents age 25 to 64, also linking them to block groups via geographica coordinates.
Merging the three sets of data, researchers found that nearly half of Salt Lake County residents enjoy a mix of food options in their neighborhoods, while 30 percent have access to at least one retail food option and the remaining 30 percent live in "food deserts"—neighborhoods with no retail food options.
"We expected to find that multiple food options in a neighborhood increases the diversity of walkable destinations and that residents living in such neighborhoods would have lower body mass indexes relative to those living in neighborhoods with no retail food options," says Zick.
"While we found this to be true, we were struck by the benefit low-income neighborhoods received from having access to at least one healthy grocery option. This has significant policy and planning implications."
According to research by Arthur C. Nelson, professor of city and metropolitan planning at the University of Utah, by 2030 about half the buildings in the U.S. will have been built since 2000. How this growth takes place will have great impact on obesity as it relates to neighborhood walkability and access to healthy food options, says Zick.