Which of the following is a limitation of BMI (body mass index) when assessing weight-related health risk?

• A. It does not distinguish between weight from fat mass and weight from lean muscle mass.
• B. It directly measures body fat percentage using skinfold thickness.
• C. It cannot be used for adults because height changes daily.
• D. It requires laboratory measurement of fasting blood glucose to be calculated.

Answer: (A)

Verified step by step guidance

1. Understand what BMI (Body Mass Index) measures: BMI is calculated using the formula \(\text{BMI} = \frac{\text{weight (kg)}}{\text{height (m)}^2}\), which provides a ratio of weight to height squared.
2. Recognize that BMI is a simple screening tool that estimates whether a person is underweight, normal weight, overweight, or obese based on population data, but it does not directly measure body composition.
3. Identify the limitation: BMI does not differentiate between weight from fat mass and weight from lean muscle mass, meaning a muscular person could be classified as overweight or obese despite having low body fat.
4. Evaluate the incorrect options: BMI does not measure body fat percentage directly (skin fold thickness is a separate method), height does not change daily in a way that affects BMI significantly, and BMI calculation does not require any laboratory tests like fasting blood glucose.
5. Conclude that the main limitation of BMI in assessing weight-related health risk is its inability to distinguish between fat mass and lean muscle mass, which can lead to misclassification of individuals' health status.