Body mass index (BMI) primarily assesses which aspect of body composition?

Body mass index (BMI) is a calculation that uses a person's weight and height to determine whether they fall within a healthy weight range. The formula is weight in kilograms divided by the square of height in meters. This straightforward ratio effectively evaluates how weight correlates with height, which helps categorize individuals into different weight categories such as underweight, normal weight, overweight, and obese.

While BMI does not directly measure body fat percentage, muscle density, or metabolic rate, it serves as a useful screening tool to assess potential weight-related health issues based on height and weight. It does not differentiate between muscle mass and fat mass, and therefore it may not give a complete picture of an individual's body composition. Nonetheless, it is widely used for its simplicity and ease of calculation, making it an essential tool in health assessments.