Nearly one in four children start kindergarten either overweight or obese, and have the greatest chance of becoming obese before third grade, according to a new study from Emory University.
A team of researchers, led by assistant professor Solveig Cunningham, found that the 14 percent of children who began kindergarten in the 1998-99 school year had four times the risk of becoming obese by eighth grade than those who started kindergarten at a normal weight. They also found that of the more than 7,700 children measured, African-American and Hispanic children, as well as those from lower socio-economic backgrounds, were more at risk for becoming obese.
"This is kind of an opportunity if we're thinking about families, about pediatricians, about interventions," Cunningham says. "The more we can pin down what the risks are and when these risks are highest, it kind of empowers us to think about the ages at which they're most important."
Overall, the researchers found that obesity appears to be established early on in life. Of all the children studied, excluding those who were already obese when they began kindergarten, the study found the greatest increase in the prevalence of obesity occurred between first and third grade, for example.
"That tells us that if we're interested in school-based interventions, then we know that we can really make an impact potentially by focusing on those ages when a lot of kids are becoming obese," Cunningham says.
And it's particularly important to study the incidence, or risk, of developing obesity, as opposed to the prevalence of obesity, because parents and pediatricians can better target different ages or other groups at a higher risk, Cunningham says.
While the prevalence of obesity provides information about the number of children who are obese at different ages and over time, knowing about the incidence of obesity, or the process of becoming obese, sheds light on how children become obese and the periods of greatest vulnerability, Cunningham says.
And the particularly cohort of children studied – those who started kindergarten in 1998-99 – was of interest because they grew up during the 1990s and early 2000s, when obesity became a more prominent health concern, the study says.
According to the Centers for Disease Control and Prevention, childhood obesity has more than tripled during the last 30 years. In 1980, for example, about 7 percent of children between the ages of 6 and 11 were obese. By 2010, that number jumped to 18 percent of the same age group.
But another of the report's findings that was particularly concerning, Cunningham says, is the fact that more than 10 percent of children started kindergarten already obese. Therefore, they were not counted in calculating obesity incidence through eighth grade – the rates of those who became obese were all in addition to that 12 percent.
"We need to focus on those very first years," Cunningham says. "If it is the case that a lot of the risk of becoming obese is being set during those very first years, before kids even come to kindergarten, then that's where we really need to understand what the risk factors might be."