Adults who stuff their mouths with the wrong foods and don’t move their muscles often gain weight and may develop health problems such as obesity and diabetes as a consequence. Now there’s new evidence about how this scenario applies to children. In kindergarten, more than one in four U.S. children is overweight or obese, according to new research published in the Jan. 30th issue of NEJM. The analysis of federal data by Dr. Solveig Cunningham and other Emory University researchers found that the pathway to obesity starts in childhood and that 37% of children are obese or overweight in eighth grade. The researchers used data collected, on about 7400 children attending kindergarten during 1998-99 school year.
In kindergarten, about 1 out of 7 of the children were overweight and on top of that 1 out 8 were obese. When the same children entered eighth grade, about 1 out 6 were overweight and 1 out of 5 were obese. The annual incidence of obesity decreased from just over 5% during kindergarten to just under 2% between fifth and eighth grade. Overweight 5-year-olds were four times as likely as normal-weight kindergarteners to become obese, with a 9-year cumulative incidence of 31.8% vs. 7.9%.
The data were collected for a study designed and conducted by the National Center for Education Statistics, the Early Childhood Longitudinal Study, which focused on the Kindergarten Class of 1998–1999 . The researchers used standard definitions of obesity (> 95th percentile for height and age) and overweight (> 85th percentile for height and age). The Centers for Disease Control and Prevention developed the standardized U.S. charts growth charts from which the percentiles were taken in 2000. The study group of nearly 7400 children is considered representative of the 3.8 million US children of kindergarten age in 1998-999. Birth weight was available for all children, and information about height and weight was collected at seven time points between 1998 and 2007. The height and weight were used to calculate body mass index (BMI) and to compare the BMI of each child to the CDC standards.
The analysis also found family income correlated with obesity. Children whose families were among the wealthiest 20% had lower prevalence of obesity in kindergarten than children from lower income families, a that trend persisted through eighth grade. At all ages, prevalence of obesity was highest among children in the next-to-poorest quintile. By eighth grade, more than a fourth were obese.
The authors’ results suggest that important components of childhood obesity for many children are established in the years before a child enrolls in school. What the roles of early-life home and preschool environments and genetics will all merit further examination and study.
In an accompanying editorial, Drs. Steven L. Gortmaker and Elsie M. Taveras wrote that the article “provides a useful perspective on early predictors of obesity incidence from kindergarten entry to grade 8” and said “risk reduction among young children is important.”
In summary, the Emory study suggests that eating the wrong foods starts young; efforts at risk reduction likely must start before children enroll in school. That message has important new implications in a nation in which obesity and diabetes are already major health problems.