Introduction: Overweight and obesity and their health consequences have been recognized as major public health problems worldwide. A significant increasing trend in the prevalence of overweight and obesity among children and adolescents has been documented over the last few decades in developed and in developing countries.  The present study attempted to identify the most common physical factors of childhood overweight and obesity.Methodology: A case control study was carried out among 310 obese (cases) and 384 non obese (control) children from selected schools of Udupi district.  Based on the BMI children were classified as obese or non-obese.  A structured questionnaire was administered to assess the physical activity level of the children.Result: The physical activity risk factors associated with childhood obesity are Less than two hours of physical education per week, sedentary activity after school hours, spending more than two hours per day in videogames and watching television, spending more than two hours per day on sedentary activity, never participating in team sports, less than two hours of vigorous physical activity per week, less than 3 sessions/week of muscle training activity. Conclusion: Sedentary lifestyle is the most common factor for childhood obesity. Measures should be initiated at the early age to prevent and control childhood obesity.