Body mass index (BMI) is a numerical value of your weight in relation to your height. It is used to determine if your weight is healthy or unhealthy. BMI is a quick, inexpensive and easy-to-perform method to check if a person is underweight, of normal weight, or overweight or obese. BMI is a good indicator of body fat but does not measure muscle mass; hence, it is not an accurate indicator for those who have a lot of muscle bulk, like body builders.
The scale is an initial indicator to help determine potential health problems if the person is of unhealthy weight. However, your doctor may perform further assessments such as evaluation of diet, measurement of skinfold thickness, physical activity, family history and other health screenings to determine associated health risks.
BMI is used to broadly define different weight groups in adults 20 years old or older.