Children who went near places that sold junk food between home and school were more likely to end up purchasing that junk food, according to a new study that used global positioning system (GPS) technology to track kids' trips for 2 weeks.
With about 650 children ages 9-13 enrolled from 25 schools in Ontario, Canada, researchers observed their movements and had them fill out a survey and a diary that identified food purchases. They found that each 1-minute increase in adolescents' exposure to unhealthy food outlets was associated with a 17% increase in the odds of buying junk food (odds ratio 1.17, 95% CI 1.14-1.21).
The significance of a 1-minute increase held after being stratified by sex -- females were slightly more likely than boys to purchase junk food, but the increases were significant for both -- and by mode of transportation, according to the authors, who were led by Richard Sadler, PhD, at Michigan State University. Sadler and colleagues published their findings this week in the Canadian Journal of Public Health.
Barry Popkin, PhD, a professor of nutrition at the University of North Carolina, told MedPage Today that it is hard in research like this to tease out what effect simple access and exposure has versus the role of marketing. "All jointly play a huge role," he wrote in an email. "But as with tobacco, we have found for that limiting access truly mattered."
He also suggested that schools should not be selling junk food to children, and that pricing incentives matter, so taxes should be part of the conversation as well.
Meanwhile, David Katz, MD, the founding director of the Yale University Prevention Research Center, observed the relationship that Sadler and colleagues found isn't necessarily causal. "The composition of a neighborhood varies with its residents, and vice versa," he told MedPage Today in an email. "The distribution of fast food outlets may be a cause, but it may also be an effect of socioeconomics. There are more such outlets in poorer neighborhoods where people are more likely to make routine use of fast food, and are less apt to be shopping in Whole Foods."
Katz added that there may be disparities in society that lead to clusters of such places in some areas while discouraging them in others.
Data were collected as part of a larger project known as the Spatial Temporal Environment and Activity Monitoring (STEAM) Project, which ran from 2010 to 2013 and included children from a various social environments. Fifty-meter "buffer zones" were calculated around each source of junk food -- including fast food, variety stores, pizza places, and ice cream shops -- and exposure was measured as time inside of that bubble. The number of minutes of exposure was capped at 17 to prevent outliers from dominating the overall results.
Most of the children (511 of 654) were exposed to some sort of junk food establishment. About 39% of kids traveled to and from school on the bus, while 31% walked or biked and 30.2% were in a car. The odds ratio for purchasing junk food associated with a one-minute increase in exposure was 1.13 (95% CI 1.06-1.20) for biking or walking and 1.22 (95% CI 1.16-1.28) for car travel; both were statistically significant. Trips by bus, however, were not significantly associated with junk food purchasing.
Kids were more likely to buy junk food returning home rather than going to school. Girls were slightly more likely to buy junk food with each increment in exposure than were boys (odds ratio 1.19 per minute, 95% CI 1.15-1.24 for girls versus 1.12, 95% CI 1.06-1.19 for boys).
Sadler and colleagues wrote that despite an agreement among most scholars that environment is important to food choices, that relationship remains "poorly conceptualized."
In addition, "Neighborhood food environments can have a particularly strong influence on children, including adolescents, who tend to be more restricted geographically than adults and who are therefore more captive to their local built environments," they wrote.
Katz wrote that many of the calories in the diet of a typical American child are from junk food. "That either means that junk foods are displacing a major proportion of calories from non-junk (i.e., actual food) or those calories are being added," he wrote. "Either is bad: If the calories are being added, then the contribution to obesity is enormous; if calories are being substituted, the direct contribution to obesity is a bit less, but the contribution to ill health is greater."
He added that what needs to be changed isn't just neighborhoods; it's the culture. "The distribution of fast food outlets is just the icing; a culture that condones feeding junk to its children is the cake," he wrote.
Limitations of the study include a lack of generalizability, since a small part of southwestern Ontario was the only area studied. Researchers cannot determine causation given the study's design, and though the GPS methods used in the study were more accurate than previous methods, it still might not encompass the totality of the child's exposure to junk food outlets. In addition, the study duration was relatively short.
"Policies and programs that mitigate the concentration of unhealthy food outlets close to schools are critical for encouraging healthy eating behaviours among children and reducing diet-related health issues such as obesity," Sadler and colleagues concluded.
The authors disclosed no relationships with industry.
Aucun commentaire:
Enregistrer un commentaire