Junk food in schools gets weighty reprieve

On-site sale of sugary snacks may not feed obesity

Controversial sales of candy, soda and other junk food in middle schools don’t weigh heavily on students’ waistlines. This surprising finding — based on a study that followed almost 20,000 kids through middle school — suggests that obesity prevention programs should target children in their homes and communities during the preschool years, when eating habits form, researchers say.

Some scientists who study childhood obesity caution that the new investigation may underestimate a tendency for students to gain weight in middle schools that offer high-calorie alternatives to standard lunches.

Boys and girls, kids from rich families and poor ones, and students of different races displayed no greater tendency to get heavier or to become obese in middle schools stocked with sugary and fatty goodies, as opposed to schools free of junk food, say sociologists Jennifer Van Hook and Claire Altman, both of Pennsylvania State University in University Park.

Their report appears in the January Sociology of Education.

“Children may face greater risks for obesity at home than at school, even if their schools sell junk food,” Van Hook says.

Kids’ eating patterns may take root well before middle school, she proposes. Also, middle school students’ structured schedules may leave little opportunity to scarf junk food during the day.

The researchers’ findings don’t exclude the possibility that some individuals find ways to eat enough junk food at school to gain weight, Van Hook adds.

She and Altman analyzed height and weight data for a nationally representative sample of 19,450 children who were fifth-graders from 2003 to 2004 and eighth-graders from 2006 to 2007, attending both grades in the same county. School principals provided information about foods available for purchase at their schools.

But principals usually don’t know what foods are available in their own schools’ vending machines and lunch lines, raising doubts about the new study’s accuracy, says nutrition scientist Mary Story of the University of Minnesota in Minneapolis. Van Hook and Altman lacked “absolutely essential” data on individual kids’ eating habits at school, which would directly show whether junk food availability led to weight gains, Story adds.

A more comprehensive national study conducted in 2004 and 2005 linked junk food sold in vending machines in or near school lunch areas with increased student body weight, Story says. She estimates that 40 percent of elementary and secondary school students in that study obtained enough daily calories, on average, from food other than school lunches to gain weight.

About 59 percent of fifth-graders and 86 percent of eighth-graders in the new analysis attended schools that sold junk food. Yet the overall percentage of overweight or obese students in the study sample decreased slightly from fifth to eighth grade, from approximately 39 percent to 35 percent. In 2008, an estimated 35.5 percent of 6- to 11-year-olds in the United States were either overweight or obese.

Even if further research confirms the new finding, epidemiologist Daniel Taber of the University of Illinois at Chicago argues, junk food sales in schools should be curtailed. Kids can adapt to anti-obesity programs that target junk food in their homes and neighborhoods by eating more of the stuff at school, he explains.

“If schools are not part of the solution to childhood obesity,” he says, “they will be part of the problem.”

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

More Stories from Science News on Humans