Prof. Hook said:
"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."
Prof. Hook and Claire E. Altman gathered data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-1999. The large study tracked the children all the way up to eighth grade. The researchers focused on a sample of 19,450 kids during the years 2003-2004 (fifth graders) and 2006-2007 (eighth graders).
Junk food was available in 86.3% of the eighth graders' schools and 59.2% of the fifth graders'.
Even though the percentage rise in junk food availability and accessibility from fifth to eighth grade was significant, the obesity/overweight rates in the two age groups remained pretty much the same. In fact, (obesity/overweight) rates dropped as the children got older - from 39.1% in fifth graders to 35.4% in eighth graders.
Van Hook said:
"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. 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."
The authors believe that authorities need to focus on the home and family environments, plus other broader non-school environments, if they want to tackle childhood obesity effectively.
Van Hook explained:
"Schools only represent a small portion of children's food environment. 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."
According to the findings in this study, combating childhood obesity/overweight is most effective when younger children are targeted.
The authors wrote:
"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," Van Hook said. "So, their middle school environments might not matter a lot."