How is body mass index (BMI) calculated and what does it indicate?

• A. BMI = weight (kg) / [height (m)]^2; used to categorize underweight, normal, overweight, or obesity.
• B. BMI = weight (lbs) / height (in)^2.
• C. BMI = body fat percentage.
• D. BMI is derived from waist circumference.

Answer: (A)

BMI relates weight to height and is used to categorize weight status. The standard calculation is weight in kilograms divided by height in meters squared. Using metric units keeps the result comparable and aligns with established thresholds; if you use pounds and inches, you’d need the conversion factor 703 to obtain the same BMI value. BMI provides a rough estimate of body fatness for most people, but it doesn’t measure body fat directly and doesn’t account for where fat is distributed or for muscle mass. Based on the result, categories are underweight (<18.5), normal weight (18.5–24.9), overweight (25–29.9), and obesity (30 or higher). The other approaches aren’t correct because BMI is not body fat percentage and it does not derive from waist circumference; it relies on height and weight with appropriate unit conventions.