Abstract

Background The researchers do not prove the effect of birth weight on childhood obesity, so far. This study aimed at providing evidence on the effect of birth weight on obesity and overweight among primary school pupils. Materials and Methods: This case-control study was conducted on 508 primary school pupils. Multistage sampling technique was applied to increase the accuracy of risk calculation. Pupils were divided into the two groups of case (170 pupils with a Z-score = 1 as overweight and obese) and control (338 pupils with a Z-score between -2 to 1 as not being obese or overweight) based on WHO reference data, For each case, two controls were matched and selected based on age, gender, and type of school. Demographic, physical activity as well as 24-hour dietary program and amount of energy expenditure data were collected. All data analyses were performed using SPSS. Odds ratio with 95 confidence interval was estimated. Results: The risk of obesity and overweight among girls who had a birth weight > 3,500g, was 2.51 times higher than that in girls with a birth weight = 3,500g (OR=2.51, 95 Cl: 1.2-5.25). However, not only this risk among boys was not higher than unity, but also it was less than one showing a reveres not-significant association (OR=0.715, 95 CI: 0. 369-1.39). Conclusion Birth weight was an independent risk factor for obesity and overweight during childhood only among girls. Gender had a moderating effect on the relation between birth weight and obesity during childhood.