The study indicates higher BMI associated with residential proximity to a fast food restaurant, and among lower-income African Americans, the density, or number, of fast food restaurants within two miles of the home.
Data was collected from a large sample of more than 1,400 African American adult participants from the Project CHURCH research study—a collaboration between MD Anderson and Windsor Village United Methodist Church in Houston.
In this study, Lorraine Reitzel, Assistant Professor in the Dept. of Health Disparities Research at MD Anderson, and her team examined two different food environment variables and their associations with BMI: proximity and density of fast food restaurants, which were based on each participant's geocoded residential address. The study participants were also broken into two income groups: those making less than $40,000 a year and those making $40,000 or more a year.
The study controlled for factors that may influence a person's BMI including gender, age, physical activity, individual household income, median neighborhood income, education, partner status, employment status, and residential tenure. Sedentary behaviors, including the amount of time the participant spent watching television, were considered. Researchers also controlled for the presence of children in the home because of its known relation with physical activity rates.
Researchers examined the density of fast food restaurants within a half mile, one mile, two miles, and five miles around each participant's home.
On average, there were 2.5 fast food restaurants within a half mile, 4.5 within a mile, 11.4 within 2 miles, and 71.3 within 5 miles of participants' homes. "We found a significant relationship between the number of fast food restaurants and BMI for within a half mile, one mile, and two miles of the home, but only among lower-income study participants," said Reitzel. The data showed the greater the density, the higher the BMI.
When examining proximity—the distance in miles from each participant's home to the closest restaurant—the study found that closer proximity was associated with a higher BMI. In fact, although results indicate that the relationship between a higher BMI and proximity was stronger for those of lower income, it was still significant in the group with the higher incomes. The data also showed that every additional mile participants' lived from the closest fast food restaurant was associated with a 2.4% lower BMI.
"There's something about living close to a fast food restaurant that's associated with a higher BMI," said Reitzel. She said that there may be some behavioral economics involved in the decision to choose fast food over a healthier choice. "Fast food is specifically designed to be affordable, appealing, and convenient. People are pressed for time, and they behave in such a way that will cost them the least amount of time to get things done, and this may extend to their food choices."