Background: The aim of this study was to identify risk factors, including the type of delivery, breastfeeding and its duration, birth weight, the timing of solid food introduction, the mother's education level at birth, and smoking status during pregnancy, that are associated with obesity in children living in Istanbul.

Methods: This study involving 4990 healthy children aged 2-14 years, at an outpatient clinic in a tertiary care hospital from June 2012 to July 2014.

Results: The overall rates of overweight and obesity in children were 13.1% and 7.8%, respectively. Results demonstrated that 44.5% of children were delivered by caesarean section. In all age groups, 7.8% of children delivered by caesarean section were obese compared with 7.9% of children born vaginally. No significant association between caesarean section delivery and obesity in childhood was found in our study [odds ratio (OR)=0.98, 95% confidence interval (CI)=0.64-2.87, P=0.454]. There was also no association between duration of breastfeeding and the introduction of solid foods before 4 months or after 6 months of age and childhood obesity (OR=0.95, 95% CI=0.69-1.3, P=0.771; OR=0.99, 95% CI=0.64-1.53, P=0.261). Regression analyses revealed that children with birth weights greater than 3801 g or those with maternal body mass index (BMI) equal to or greater than 30 had an increased risk of being obese or overweight (OR=1.78, 95% CI=1.19-2.65; OR=3.95, 95% CI=1.94-5.81).