Junk Food Availability in Schools Raises Obesity

Schools that are under financial pressure are more likely to make junk food available to their students.

Researchers and public health officials are currently at a loss to explain the rapid rise in weight problems among children and adolescents that began in the 1980s. Concerns about the long-term health consequences of overweight have ignited a debate about school policies that make junk food available to students in school. While the revenues generated by in-school junk food sales fund a wide variety of discretionary school programs, some school district officials consider the link between junk food and overweight intuitively plausible. They have instituted policies to ban or reduce access to junk food despite the fact that little is known about whether access to junk foods in school really does contribute to obesity.

In Reading, Writing and Raisinets: Are School Finances Contributing to Children's Obesity? (NBER Working Paper No. 11177), co-authors Patricia Anderson and Kristin Butcher combine data from several sources to examine both the effect of financial pressure on school food policies and whether these school food policies help create overweight adolescents. They find that schools that are under financial pressure are more likely to make junk food available to their students, to have "pouring rights" contracts, and to allow food and beverage advertising to students. By using measures that capture financial pressure to predict the fraction of schools in a county with these particular food policies, they then estimate the effect of the fraction of schools in a county with these food policies on adolescent body mass index (BMI).

They find that it is the actual availability of junk food, rather than advertising or pouring rights, that is associated with weight gain. In general, "a 10 percentage point increase in the proportion of schools with junk food is correlated with about a 1 percent higher BMI for the average student."

The authors caution that their results do not imply that every student who can buy junk food at school will suffer from overweight. The effect of junk food availability is statistically different for adolescents whose parents are overweight. Access to junk food in school has no effect on the 44 percent of students whose parents have normal weights. For those with an overweight parent, who may have a genetic susceptibility to weight gain, a 10 percent increase in the proportion of schools that make junk food available increases BMI by more than 2 percent.

Though junk food at school may pose a health risk to some students susceptible to obesity, existing junk food policies help generate funds for programs that benefit all students, Anderson and Butcher note. They further point out that the substitute foods allowed by official policies banning junk food and soda often allow products, like fruit juice, that contain just as many calories. The authors recommend that officials considering a change in school food policies weigh the health costs borne by the fraction of students susceptible to obesity against the benefits conferred by the programs funded by in-school junk food sales

-- Linda Gorman