Researchers from Emory University in Atlanta, GA, conducted a study that suggests children who are overweight or obese by kindergarten are four times more likely to be obese in eighth grade, compared with their normal-weight counterparts. Focusing obesity-prevention efforts on younger children may be important, the team says.
Led by Solveig A. Cunningham, assistant professor from Emory, the researchers published their results in the New England Journal of Medicine.
They note that prevalence of a body mass index (BMI) at the 95th percentile or higher in children between 6 and 11 years old increased from 4.2% in the 1960s to 15.3% in 1999-2000.
Although increasing childhood obesity in the US has been detailed in adolescents, not much is known about incidence of the growing issue in younger children.
So, the team analyzed data on children from the Early Childhood Longitudinal Study of the US Kindergarten Class of 1998-1999. This was a representative prospective cohort of 7,738 children in the US, whose height and weight were measured seven times between 1998 and 2007.
Of these children, 6,807 were not obese at the baseline of the study. The team used thresholds from the Centers for Disease Control and Prevention (CDC) for what constituted "overweight" and "obese."
'First 5 years of life important'
The researchers found that when the children entered kindergarten at an average of 5.6 years, 12.4% were obese and a further 14.9% were overweight. By the time this group entered eighth grade at an average of 14.1 years, 29.8% were obese and 17% were overweight.
The children who were overweight in kindergarten were four times more likely to become obese by eighth grade, compared with children who were at a normal weight.
Additionally, the results showed that children who were large at birth and overweight by kindergarden had the highest risk of becoming obese before the age of 14.
Commenting on the findings, Cunningham says:
"We have evidence that certain factors established before birth and during the first 5 years are important. Obesity prevention efforts focused on children who are overweight by 5 years old may be a way to target children susceptible to becoming obese later in life."
Study 'provides insights into epidemic'
In their analysis, the researchers also assessed obesity risks among different socioeconomic and ethnic backgrounds.
They found that overweight children from the two highest socioeconomic groups had an obesity risk five times higher than normal-weight children of a similar socioeconomic status.
But overweight children from the lowest socioeconomic group had an obesity risk that was only 3.4 times higher than normal-weight children from this group.
Additionally, obesity was higher among Hispanic children than non-Hispanic white children at all ages, while non-Hispanic black children had a higher rate of obesity than non-Hispanic white children, starting in third grade.
"Examining incidence may provide insights into the nature of the epidemic, the critically vulnerable ages, and the groups at greatest risk for obesity," the researchers write.
Medical News Today recently reported on a "growing class gap" in teen obesity in the US. The study suggested that teens in poorer families have increased rates of obesity, possibly due to lifestyle factors.