Question

Identifying independent and dependent variables?

I am having trouble identifying the independent and dependent variables. I read a study that was conducted in order to determine the levels and patterns of physical activity of obese and nonobese children using accelerometers. This study will help researchers gain a better understanding the relationship of physical activity (frequency, intensity, and volume) and obesity. I know, BMI was also used in the study. Please help me identify what the independent and dependent variables are!!

Thanks!