The neighborhood availability of energy-dense snack foods within 1 kilometer of an individual’s residence was positively associated with BMI, after controlling for individual- and household-level characteristics. An additional 100 meters of shelf-space for snack foods was associated with an increase in 0.1 BMI units. At this rate, an increase equivalent to 1 SD in the neighborhood shelf-space of energy-dense snack foods would translate to about two extra pounds for a person who is 5′5″. Positive associations were also found when availability was disaggregated into specific types of snack foods, that is, when salty snacks, candies, and carbonated beverages were analyzed separately. There were no significant associations of BMI with the availability of fruits and vegetables.
Other public health research has reported associations between the food environment and weight status among area residents, with inverse associations between supermarket availability and BMI or obesity,6–8
and positive associations between convenience store availability and overweight status.7,8
The premise of this store-based literature is that the presence of a supermarket increases access to healthy food, allowing residents to achieve a better weight status from improved dietary consumption. The corollary is that convenience stores provide an excess of unhealthy foods, making it more difficult for residents to control their weight status. This research tests the availability dimension directly by assessing the total amount of shelf-space of fruits and vegetables and energy-dense snack foods. Although there is no other literature with which to compare the associations between food availability and BMI, the results are consistent with the premise and findings from previous store-based research.
This approach allows for an assessment of the cumulative contributions to food availability from various store types. Small and medium grocers often have positive amounts of fruits and vegetables, and their easy accessibility might allow for fill-in shopping in urban areas with a distant supermarket.16
Moreover, the marketing literature has long shown that shelf-space is the relevant concept for driving consumer purchase decisions. Although area residents might not shop in all stores within a given radius of their house, greater shelf-space availability in this area implies more options about when and where to shop for specific foods, such as on the way home from work or on the way to visiting a neighbor’s house.
Why then do the current results not show an inverse association between availability of fruits and vegetables and BMI? Unlike snack foods, the purchase of fruits and particularly vegetables is more likely to be planned than impulsive, because they typically require cooking or preparation. It has been argued17
that salience, or seeing a food, can stimulate unplanned consumption. Energy-dense snack foods were much more available at 1 kilometer than fruits and vegetables, and snack foods are more frequently placed at cash registers. These cues could have led to more impulse purchases and greater consumption of energy-dense foods.
Second, consistent with this argument, the results do show negative, although not significant, coefficients on the fruit and vegetable availability measures at 2 kilometers (). Perhaps residents did mostly planned purchases of fruits and vegetables at supermarkets, so the wider radius was more relevant for this food group. About three times as many respondents had a supermarket within 2 kilometers of their house than within 1 kilometer. Finally, price may be more important for planned purchases than impulsive buys. Supermarkets not only have a greater availability of fruits and vegetables, but their prices for these foods are often lower than those in small groceries.18
The lack of information on price data from these stores is certainly one limitation to this study.
Another limitation is that the study is cross-sectional. Thus, associations seen between access and BMI cannot be attributed to causality. Individuals were not randomly assigned to housing locations. Rather than the environment affecting food choices, individuals with given food preferences could have chosen to move to specific food environments. Although this argument could certainly be raised as a limitation to this study, mobility in Louisiana, prior to Hurricane Katrina (when this study was conducted), was relatively low. Census data from 2000 show that 79% of people living in Louisiana were born there, the highest rate in the country.19
Outcome measures were also based on self-report. Women are known to understate their weight, and men to overstate their height.20,21
Both errors result in a lower BMI than the true value, and mean BMIs in this dataset are lower than national averages. However, there is no reason to believe that these biases would be systematically associated with geographic variables, such as distance to specific store types.
The results presented here come from a phone survey based on a sample of listed landlines. Compared to residents in the overall population from which this sample was drawn, the sample consists of those who are slightly older, with more women, fewer African Americans, and a higher average household income. However, regression models have controlled for these variables, so a sampling bias is not likely to affect the overall conclusions. Of more potential concern are unobserved differences caused by the unavoidable exclusion of households without landlines. Although recent research22
suggests that binge drinking and smoking behaviors are more prevalent among “cell phone only” adults, it is unknown if these individuals react differently to food environments than others, and if they do, whether such differences would strengthen or weaken conclusions presented here.
A number of studies have shown associations between access to specific retail outlets and BMI/obesity. This study indicates an association of BMI and obesity, albeit modest, with specific types of foods. This type of finding, if supported by additional research, might be more easily amenable to policy action. It is not a simple matter to increase the number of supermarkets in underserved areas. Supermarkets operate at very narrow margins, so profitability limits entry into some areas. There may, however, be potential to change the shelf-space configurations of successful small stores currently operating in low-income neighborhoods. Various initiatives have been suggested23,24
to achieve such change, from taxation of snack foods to incentives to increase healthy food offerings. If successful, these policy changes could improve the neighborhood food environment and offer better conditions for those seeking to address energy imbalance.