THURSDAY, May 16, 2013 (HealthDay News) -- Having a fast-food restaurant nearby might be a convenience, but living within two miles of one may be a little too convenient.
According to a new study, black Americans who live near these businesses have a higher body-mass index than those living farther away.
Researchers at the University of Texas M.D. Anderson Cancer Center found this was particularly true for those with a lower income. Body-mass index (BMI) is a measurement of body fat that takes into account a person's height and weight.
The findings are significant because black people are at greater risk for the negative health effects associated with obesity, such as diabetes and heart disease, the study authors pointed out.
"According to prior research, African-Americans, particularly women, have higher rates of obesity than other ethnic groups, and the gap is growing," study leader Lorraine Reitzel, an assistant professor in the department of health disparities research at M.D. Anderson, said in a university news release.
"The results of this study add to the literature indicating that a person's neighborhood environment and the foods that they're exposed to can contribute to a higher BMI," she said.
"We need to find the relationships and triggers that relate to this population's BMI, as they're at the greatest risk for becoming obese and developing associated health problems. Such information can help inform policies and interventions to prevent health disparities," Reitzel explained.
The study involved more than 1,400 black adults divided into two groups: those making less than $40,000 per year and those making $40,000 or more per year. The researchers considered whether or not the participants had children, and took into account gender, age, physical activity and education, along with other factors that could influence their BMI.
The investigators also analyzed how close the participants lived to fast-food restaurants and the number of those restaurants within a half-mile, one mile, two miles and five miles of where they lived.
"We found no previous research literature that considered household income when investigating whether there were associations between fast food availability and BMI," noted Reitzel.
The study revealed that, on average, there were 2.5 fast-food restaurants within a half-mile of the participants' homes. In addition, there were an average of 4.5 of these restaurants within one mile, 11.4 within two miles and 71.3 fast food restaurants within five miles of their homes.
Living closer to a fast-food restaurant was associated with a higher BMI -- regardless of the participants' income, the study showed. On the other hand, every additional mile between the participants' homes and the closest fast-food restaurant was associated with a 2.4 percent lower BMI.
The study also found that the more of these restaurants within a particular area, the higher the participants' BMI. The researchers pointed out there was no significant association for the five-mile area.
"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," noted Reitzel.
"There's something about living close to a fast-food restaurant that's associated with a higher BMI," she pointed out. However, an association does not prove a cause-and-effect relationship.
"Fast food is specifically designed to be affordable, appealing and convenient," Reitzel explained. "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."
The study authors noted lower-income residents may not have access to transportation, so having fast-food restaurants close to home might be easier.
"This may also be why there were significant associations for density and BMI within two miles of the home, which is an easily walkable distance, but not five miles of the home," said Reitzel.
In other cases, residents of neighborhoods with fewer roads may be tempted to eat from the restaurants they pass every day. "Those visual cues may prompt people to choose fast food even when it was not the original intent," added Reitzel.
The study was published online May 16 in the American Journal of Public Health.
The U.S. Centers for Disease Control and Prevention has more about fast-food consumption among U.S. adults.