Background and Objective: Childhood obesity is considered a major health problem in both developed and developing countries. Regarding the impact of obesity on children, family and society, the aim of this study was to determine the prevalence of obesity and its correlation with life style and possible risk factors among preschool children in Zanjan.

Materials and Methods: This cross-sectional study was conducted on 890 children aged 2-5 years old who were randomly recruited from child care centers of Zanjan city. Weight, height and the body mass index (BMI) of all participants were measured and a questionnaire consisting of birth history, feeding pattern, family history of obesity and diabetes, sleep and activity times were filled by interviewing with parents. Data were analyzed by SPSS software.

Results: The prevalence rate of obesity was10.9% and overweight prevalence was12.9%. There was no significant difference between two sexes (p=0.379). But there was a significant relationship between obesity and preterm delivery, birth weight, formula or cow milk feeding. Family history of obesity, physical activity, time spent watching TV and computer games per day, consumption of snacks and use of fast food during the week were all taken into account.

Conclusion: The findings indicate that obesity is high in preschool children in Zanjan city. Considering its significant correlation with physical activity, nutrition and birth weight, it seems that training programs and changes in the lifestyle and nutrition could have beneficial effects on the prevention and reduction of childhood obesity.