What is body mass index (BMI)?

• A. A measure of body fat based on height and weight
• B. A test to diagnose dehydration
• C. A way to calculate daily protein needs
• D. A scale that estimates metabolic rate

Answer: (A)

BMI is a quick screening measure of body fatness that uses only height and weight. It is calculated by dividing a person’s weight in kilograms by the square of their height in meters. This simple ratio helps flag whether someone falls into categories that are linked to higher health risks, such as underweight, overweight, or obesity, which can guide further evaluation. However, BMI is not a direct measure of body fat; it doesn’t distinguish fat from muscle, and factors like athletic muscle mass, age, and ethnicity can affect interpretation. That’s why BMI is used as a screening tool rather than a precise diagnostic test. It doesn’t assess dehydration, protein needs, or metabolic rate—that requires other assessments.