Incidence and Prevalence of Childhood Obesity in Tehran, Iran in 2011.

Background: The aim of this study was to determine the incidence and prevalence of obesity in Tehranian children.

Methods: Data from children participated in Tehran Lipid and Glucose Study (TLGS) were evaluated. Cut off points for definition of obesity was the CDC's standard thresholds of the 95th percentile and 85th percentile for overweight. Prevalence, annual incidence of obesity, cumulative incidence over 10 year and the incidence density (cases per person-years) totally were calculated.

Results: The annual incidence of obesity was 1.9 and 3.4% per year in the first 3 yr and decreased to 0.9 and 2.5% in the last 3 yr of follow-up in girls and boys, respectively. Incidence density rates were in line with cumulative incidence, with a rate of 20.7 per 1000 person-years between the ages of 5.6 and 15.5 yr. The prevalence of obesity was higher among children who had obese parents ( P =0.03). Among all ages, across the quartiles of parents' BMI, the prevalence of obesity increased with rising in paternal ( P =0.001) or maternal BMI ( P =0.004). Physical activity of mothers affected the prevalence of obesity in children at mean ages of 5.3 and 9.1 yr. Across quartiles of mother's physical activity, from heavy to light, the prevalence of obesity increased among children, from 4.4% to 5.9% in children, aged 5.3 ( P =0.02) and from 11.6% to 13.0% in children, aged 9.1 yr ( P =0.03).

Conclusion: Prevalence of obesity among children increased with age. Cumulative incidence of obesity in children who were overweight at baseline was much higher than other children.