Childhood obesity has become one of the most serious health challenges of today's world. Food preferences, physical activity status, family, and school offerings of the child play an active role in the development of obesity. This study aimed to determine the body composition of children aged six to nine years and to evaluate the possible factors causing obesity such as food consumption and physical activity. The study was conducted in İstanbul, Üsküdar with 371 primary school students and their parents. Separate questionnaires including food consumption, physical activity, sleep, and breastfeeding were applied to students and their families. Of the children, 13.7% (n=51) were overweight and 23.2% (n=86) were obese. Body mass index (BMI) of children was found to have a positive correlation with the body weight of their parents, childbirth weight, and time spent on computer/television whereas it had a negative correlation with sleep duration (p<0.05). Body fat percentage was found to be lower in children of high-income families (p<0.05). Children found to be overly consuming foods such as wafers, chocolates, and candy. In conclusion, the factors causing obesity in children should be evaluated as a whole, they should be developed for the health improvement, and parents, children, and staff in schools should be trained in this regard.