OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Why is BMI not an accurate measure of an individual's fitness level?

1. It does not consider dietary habits

2. It assesses both fat and muscle equally

3. It assesses the ratio of fat to muscle, not overall fitness

4. It is based solely on weight

The correct answer is: It assesses the ratio of fat to muscle, not overall fitness

BMI, or Body Mass Index, is a widely used metric that calculates an individual's weight in relation to their height. While it can indicate whether a person is underweight, normal weight, overweight, or obese, it does not provide a complete picture of an individual’s fitness level because it does not differentiate between fat mass and muscle mass. Muscle is denser than fat, meaning that someone with a high muscle mass may be classified as overweight or obese according to BMI, even though they may have low body fat percentage and be quite fit. Conversely, a person with a lower muscle mass but higher body fat could be classified as having a healthy BMI, despite being unfit. Therefore, BMI fails to assess crucial aspects of fitness, including muscle strength, endurance, cardiovascular health, and overall physical performance. In essence, while BMI can provide some insight into body composition from a statistical viewpoint, it does not accurately reflect an individual's fitness or health, as it overlooks the important distinction between fat and muscle.