ABSTRACT
Since the prevalence and severity of childhood obesity is increasing, understanding the effective factors for prevention of this disorder is important. A total of 513 students of both sexes in the first year of primary schools, were recruited in this cross-sectional study. They were chosen randomly from 19 regions [of the ministry of education] from Tehran city. Their weight and height were measured, and information on infant birth and feeding characteristics [birth order, birth weight, the type of feeding in infancy, the duration of exclusive breast feeding, the duration of breast feeding and formula feeding] activity levels, the timing of the introduction of complementary foods were obtained. Descriptive statistical methods such as frequency distribution table,%C2 test and central and dispersion parameters were used to describe samples. Eight percent of the children were overweight and 11.7% were obese. There was no significant relation between the type of feeding [breast or formula feeding] and children's BMI. The duration of breast feeding was not significantly associated with children's BMI, Children's BMI had a negative linear association with the duration of exclusive breast feeding [r=-0.151, P=0.0001]. The duration of formula feeding was associated with children's BMI [r=0.108, P=0.007]. Children's BMI had an inverse linear relation with the time of introduction of complementary foods [r=-0.128, P=0.002]. This study shows the importance of duration of breast feeding in reducing the risk of childhood obesity