© 2021, Galenos. All rights reserved.Introduction: Obesity has become a serious health concern worldwide. Risk factors of obesity are different in urban and rural areas. The aim of this study was to determine the risk factors related to obesity and being overweight among children in low and high socio-economic groups in a big metropolitan city, Istanbul. Materials and Methods: A cross-sectional study was carried out on 490 school-age children between 5 and 15 years. Low and high socio-economic groups were determined according to socio-economic status (SES). Socio-demographic characteristics of children were collected from the parents. Results: The effect of having frequent snacks rich in carbonhydrates (p=0,001) and sedentary lifestyles (p=0,001) on BMI was significant in both SES groups. In high SES group, BMI of the <10 years boys was significantly higher than that of the <10 years girls; Boys also had higher BMI at both age groups of either younger or older than 10 years. In low SES group, girls were significantly more overweight than boys. High family income, high paternal BMI and consuming energy rich products increased the obesity risk in children 1,560 times (OR: 1,560, %95 CI: 1,046-2,326), 2,015 times (OR: 2,015, %95 CI: 1,092-3,720), and 4,33 times (OR: 4,330, %95 CI: 2,897-6,472), respectively. Conclusions: As conclusion, high family income, high paternal BMI and consuming energy rich products incre-ased the obesity risk. We suggest that every community has own characteristics but boys tend to have high BMIs in families with high SES.