The obesity rate for the US adult population comes from the Behavioral Risk Factors Surveillance System, created by the Centers for Disease Control and Prevention. For the purpose of this estimate, obesity is defined as a body mass index (BMI) above 30. In practice, BMI is not a diagnosis but rather a screening method for obesity, since it is based on height and weight alone rather than fat mass and location. For example, it does not account for increased muscle and bone mass in lean, athletic people. The BMI cutoffs for obesity may also be more or less predictive of health depending on race, ethnicity, gender, and height.