Define BMI and its limitations as a measure of body composition.

• A. BMI measures bone density.
• B. BMI = weight (kg) / height (m)^2; it does not differentiate fat from lean mass, fat distribution, or metabolic health.
• C. BMI directly measures body fat percentage.
• D. BMI accounts for age and gender when assessing metabolic health.

Answer: (B)

BMI is a simple index that uses height and weight to estimate body fatness and categorize weight status. The calculation is straightforward: weight in kilograms divided by height in meters squared. This makes it quick and easy to screen large groups and spot potential weight issues.

But BMI has important limits. It does not differentiate fat from lean mass, so someone with a lot of muscle may have a higher BMI even if their body fat is low. It also doesn’t indicate where fat is distributed; fat concentrated around the abdomen carries different health risks than fat in other areas, and BMI won’t reflect that nuance. Finally, BMI doesn’t measure metabolic health on its own—normal-weight individuals can have unfavorably high body fat percentage or poor metabolic markers, while some people with higher BMI may be metabolically healthy. Because it overlooks these factors, BMI is best used as a quick screening tool in combination with other assessments of body composition and metabolic health.