What is Body Mass Index, or BMI?

Body mass index (BMI) is:

• A practical measure used to determine overweight and obesity
• A measure of weight in relation to height that is used to determine weight status
• The most widely accepted method used to screen for overweight and obesity in children and adolescents because it is relatively easy to obtain the height and weight measurements needed to calculate BMI, measurements are non-invasive and BMI correlates with body fatness.

While BMI is an accepted screening tool for the initial assessment of body fatness in children and adolescents, it is not a diagnostic measure because BMI is not a direct measure of body fatness.

Source: Centers for Disease Control and Prevention "Use of BMI to Screen for Overweight and Obesity in Children"