Background: Researchers have focused on obesity as a multidimensional phenomenon and its incidence may be affected by some biological, cultural and social factors. The aim of the present study was to examine the relationship between obesity, physical activity and socioeconomic status among girl students living in northern Tehran.

Materials and Methods: In this descriptive study, 488 elementary students (7-11 years) were randomly selected from elementary schools in northern Tehran (Shemiranat district). The waist and hip circumferences, height and weight of subjects were measured using the standard methods. Body mass index (BMI) percentage was calculated through CDC2000. Nicolas Barbosa questionnaire consisting students' demographic information and the physical activity levels were completed by subjects. The data were analyzed using Pearson correlation.

Results: While a negative correlation was detected between BMI and physical activity (P<0.025), there was a significant correlation between socioeconomic status and BMI (P<0.013) and between socioeconomic status and physical activity (P=0.001).

Conclusion: Considering the importance of daily physical activity in the prevention of obesity among children, it is highly recommended.