Are Junk Food Sales in U.S. schools Responsible for Childhood Obesity?

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Between the early 1970s and late 2000s, the percentage of obese children in the United States tripled.  This trend is often attributed to the types and amounts of foods and drinks available to children, including those offered for sale in schools. Currently, the vast majority of middle schools sell competitive foods to students through one or more venue including vending machines, school stores, canteens or a la carte in the cafeteria. “Competitive foods” are sold in competition with the National School Lunch and National School Breakfast Program, and often include items such as soft drinks, juice, candy bars, potato chips, cookies and doughnuts.

In response to the childhood obesity epidemic, children’s health advocates have pressured schools to eliminate vending machines or restrict the placement, contents, and access children have to vending machines and competitive foods. However, our research along with an lot of other people’s research suggests that—at least for middle school students—this strategy is unlikely to have much impact.

The study I conducted with my PhD student, Claire E. Altman, finds that weight gain has nothing to do with the candy, soda, chips, and other junk food they can purchase at school.  We used data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-1999, which follows a nationally representative sample of students from the fall of kindergarten through the spring of eighth grade. This was a time during which school districts were just starting to remove vending machines and snack foods from schools.  The strength of our research was that we had access to a very large sample of children (19,450) and we were able to follow children over time as they progressed from fifth to eighth grade.  This enabled us to determine how much children gained weight during early adolescence, and whether weight gain depended on the type foods sold in their schools.  Most studies on this topic examine children at only one point in time (e.g., 8^th grade only) and are therefore unable to tell whether children become overweight by attending schools that sell junk food, or whether heavier children are just more likely to attend such schools in the first place.

We found that 59.2 percent of fifth graders and 86.3 percent of eighth graders in their study attended schools that sold junk food. But, while there was a significant increase in the percentage of students who attended schools that sold junk food between fifth and eighth grades, there was no rise in the percentage of students who were overweight or obese. In fact, despite the increased availability of junk food, the percentage of students who were overweight or obese actually decreased slightly from fifth grade to eighth grade.   Additionally, we found no difference in weight gain between children attending a school that sold junk food and other children.

This seems to defy common sense.  After all, we all know that children who eat junk food and soda are more likely to gain weight.  But to understand what is going on, we need to take into consideration all of the places where children eat. Schools only represent a portion of children’s food environment. Children can get food at home and their neighborhoods, and many children can walk down the street from the school to buy food. Additionally, children are actually very busy at school, so there isn’t much opportunity for them to eat while they’re in school, or at least snack endlessly, compared to when they’re at home.  School days are scheduled from beginning to end, including time spent eating. This differs considerably from home environments, where mealtimes are less regular, eating blends with other activities such as TV viewing, opportunities for snacking are greater, and food consumption is less closely monitored, especially for children staying home alone.  This is backed up by other research showing that children actually gain more weight during the summer months than during the school year.  All of this suggests that school environments may actually be protective against obesity compared to homes and neighborhoods.

It is also important to take into account children’s development. Children’s food preferences and eating habits are firmly established early in life, so middle school environment may not matter as much.  Early childhood experiences and home environments have profound effects on children’s dietary patterns.  For example, some research suggests that children can lose the ability to self-regulate food consumption (and stop eating when full) in early childhood, largely as a consequence of child feeding practices. This suggests that when it comes to combating childhood obesity and weight issues, policymakers should put more emphasis on younger children.

What does this mean for educators today? Most important, it suggests that the childhood obesity problem cannot be placed solely in the hands of schools.  A coordinated response among educators, health care workers, parents, businesses, and government is probably required.  This message may come as a disappointment to those hoping for an easy solution.  After all, schools seem to be natural places in which to enact cost-effective interventions on children. But disappointingly, schools do not seem to be effective in drastically changing a student’s weight, and the elimination of junk food sales in schools is unlikely to make much of a dent in the child obesity epidemic.  The challenge is to develop interventions that reach into the home and community.  Perhaps those interventions can start with schools, but they must reach beyond them to be effective.

Written by Jennifer Van Hook