Body Mass Index (BMI) is a number calculated from a person’s weight and height. BMI provides an indicator of body fatness for most people. It is commonly used to screen for inadequate or excessive weight that may lead to health problems.
Body Mass Index does not measure body fat directly. Instead, BMI is based on direct measures of body fat using data obtained with very accurate measurements, such as underwater weighing. BMI is an inexpensive and easy-to-perform alternative for direct measures of body fat.
BMI is not a diagnostic tool. BMI is used as a screening tool to identify possible weight problems for adults. For example, people with significant muscle mass often have a high BMI yet have little body fat. To determine if weight is excessive, and if it is a health risk, a medical professional needs to perform further assessments including evaluations physical activity, family history, diet, and other appropriate health screenings.