Past studies have suggested a relationship between neighborhood characteristics and obesity, as well as a connection between obesity and advertisements on television and in magazines.
Now, new research from UCLA has identified a possible link between outdoor food ads and a tendency to pack on pounds. The findings, researchers say, are not encouraging.
In a study published online in the peer-reviewed journal BMC Public Health, Dr. Lenard Lesser and his colleagues suggest that the more outdoor advertisements promoting fast food and soft drinks there are in a given census tract, the higher the likelihood that the area's residents are overweight.
"Obesity is a significant health problem, so we need to know the factors that contribute to the overeating of processed food," said Lesser, who conducted the research while a Robert Wood Johnson Foundation Clinical Scholar at the UCLA Department of Family Medicine and UCLA's Fielding School of Public Health.
"Previous research has found that fast food ads are more prevalent in low-income, minority areas, and laboratory studies have shown that marketing gets people to eat more," said Lesser, now a research physician at the Palo Alto Medical Foundation Research Institute in California. "This is one of the first studies to suggest an association between outdoor advertising and obesity."
For the study, the researchers looked at two densely populated areas in Los Angeles and New Orleans, each with more than 2,000 people per square mile. They focused on more than 200 randomly selected census tracts from those two areas, which included a mixture of high- and low-income residents.
They team used data on outdoor food advertising in those areas gleaned from a previous study on ads and alcohol consumption (which had tracked all the outdoor ads). They then linked that information with telephone-survey data from the same study, in which nearly 2,600 people between the ages of 18 and 98 from those areas were asked health-related questions in addition to questions about their height, weight, self-reported body mass index (BMI) and soda consumption.
The researchers found a correlation: The higher the percentage of outdoor ads for food, the higher the odds of obesity in those areas.
"For instance, in a typical census tract with about 5,000 people, if 30 percent of the outdoor ads were devoted to food, we would expect to find an additional 100 to 150 people who are obese, compared with a census tract without any food ads," Lesser said.
Given that the study focused on only two areas, the authors urge further research to determine if the findings would be replicated in other areas. Because the study was cross-sectional, the researchers do not claim that the ads caused the obesity. They also note that self-reported information about weight is subject to recall bias, and people often under-report their true weight.
But this study suggests enough of a link between outdoor food advertising and "a modest, but clinically meaningful, increased likelihood of obesity" to warrant further examination, the researchers conclude.
"If the ... associations are confirmed by additional research, policy approaches may be important to reduce the amount of food advertising in urban areas," the researchers write, while noting that outright bans on such ads might be deemed unconstitutional. "Innovative strategies, such as warning labels, counter-advertising, or a tax on obesogenic advertising should be tested as possible public health interventions for reducing the prevalence of obesity."