Weight gain has nothing to do with candy, soda, chips and other junk food, at least for middle school students, say researchers in the US who admit to being surprised by the result.
"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, professor of sociology and demography at Pennsylvania State University who led the study.
This despite the fact that the number of obese children in the US may have tripled between the early 1970s and the late 2000s.
The study relies on data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-1999, through the spring of eighth grade (the 1998-1999 through 2006-2007 schools years), the journal Sociology of Education reports.
Van Hook and her co-author Claire E. Altman, sociology and demography doctoral student at Pennsylvania, used a sub-sample of 19,450 children who attended school in the same county in both fifth and eighth grades (the 2003-2004 and the 2006-2007 school years), according to a Pennsylvania statement.
The authors found that 59.2% of fifth graders and 86.3% of eighth graders in their study attended schools that sold junk food.
But, while there was a significant increase in the%age of students who attended schools that sold junk food between fifth and eighth grades, there was no rise in the%age of students who were overweight or obese.
In fact, despite the increased availability of junk food, the%age of students who were overweight or obese actually decreased from fifth grade to eighth grade, from 39.1% to 35.4%.