Final answer:
BMI does not differentiate between fat mass and muscle mass, leading to potential misclassification of body weight status in groups like athletes and older adults.
Step-by-step explanation:
Body mass index (BMI) is commonly used to classify individuals in terms of weight and body fat. However, BMI calculations are based only on height and weight, which can be misleading because they do not account for fat mass or muscle mass. For instance, athletes with high muscle density might be wrongly categorized as overweight or obese because muscle weighs more than fat. Similarly, older adults with osteoporosis might have a lower BMI despite having a higher body fat percentage. Thus, while BMI is an inexpensive tool correlating with disease risk, it is not intended to accurately differentiate between fat and fat-free mass. Additional measurements are necessary to effectively assess body composition and health risks.