A new study suggests that, for middle school students, candy, soda, chips, and other junk food they can purchase at school has nothing to do with weight gain.

"We were really surprised by that result and, in fact, we held back from publishing our study for roughly two years because we kept looking for a connection that just wasn't there," said Jennifer Van Hook, a Professor of Sociology and Demography at Pennsylvania State University and lead author of the study, which appears in the January issue of Sociology of Education.

Van Hook and coauthor Claire E. Altman, a sociology and demography doctoral student at Pennsylvania State University, followed 19,450 national children from the fall of kindergarten through the spring of eight grade.

The researchers 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 large increase in the percentage of students who attended schools that sold junk food in the fifth and eighth grades, there was no increase in the percentage of students who were overweight or obese.

Contrary to the authors’ beliefs, despite the rise in availability of junk food, the percentage of students who were overweight or obese decreased from fifth grade to eighth grade, from 39.1 percent to 35.4 percent.

"There has been a great deal of focus in the media on how schools make a lot of money from the sale of junk food to students, and on how schools have the ability to help reduce childhood obesity," said Van Hook.

"In that light, we expected to find a definitive connection between the sale of junk food in middle schools and weight gain among children between fifth and eighth grades. But, our study suggests that—when it comes to weight issues, we need to be looking far beyond schools and, more specifically, junk food sales in schools, to make a difference."

Van Hook suggests that controlling weight gain and preventing obesity should be addressed at home.

"Schools only represent a small portion of children's food environment," said Van Hook.

"They can get food at home, they can get food in their neighborhoods, and they can go across the street from the school to buy food. Additionally, kids are actually very busy at school. When they're not in class, they have to get from one class to another and they have certain fixed times when they can eat. So, there really isn't a lot of opportunity for children to eat while they're in school, or at least eat endlessly, compared to when they're at home. As a result, whether or not junk food is available to them at school may not have much bearing on how much junk food they eat."

The researchers also suggest that childhood eating habits have a big influence on adulthood diets.

"There has been a lot of research showing that many children develop eating habits and tastes for certain types of foods when they are of preschool age, and that those habits and tastes may stay with them for their whole lives," said Van Hook.

"So, their middle school environments might not matter a lot."