(HealthDay News) — Incident childhood obesity is more likely to occur at younger ages, with overweight 5-year-olds four times as likely to become obese compared to their normal-weight peers, according to research published in the January 30 issue of the New England Journal of Medicine.

Solveig A. Cunningham, PhD, from Emory University in Atlanta, and colleagues report on the national incidence of obesity among elementary-school children using data from a representative prospective cohort of 7,738 participants from the Early Childhood Longitudinal Study, Kindergarten Class of 1998 to 1999. Height and weight were measured seven times between 1998 and 2007. Of the participants, 6,807 were not obese at baseline and were followed for 50,396 person-years.

The researchers found that 12.4% of children were obese and 14.9% were overweight when they entered kindergarten (mean age, 5.6 years). At a mean age of 14.1 years, in eighth grade, 20.8 and 17.0%, respectively, were obese and overweight. There was a decrease in the annual incidence of obesity from 5.4% during kindergarten to 1.7% between fifth and eighth grades. Compared with normal-weight 5-year-olds, those who were overweight were four times as likely to become obese (nine-year cumulative incidence, 31.8 versus 7.9%), with rates of 91.5 and 17.2 per 1,000 person-years, respectively. Of those children who became obese between the ages of 5 and 14 years, 75% had been above the 70th percentile for body mass index and nearly half had been overweight at baseline.

“Incident obesity between the ages of 5 and 14 years was more likely to have occurred at younger ages, primarily among children who had entered kindergarten overweight,” the authors write.

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