What does body mass index (BMI) measure?

Body mass index (BMI) is a widely used measurement that utilizes an individual's height and weight to estimate body fat and assess the level of obesity. It is calculated by taking a person's weight in kilograms and dividing it by the square of their height in meters. This formula provides a numerical value that categorizes individuals into various weight classifications such as underweight, normal weight, overweight, and obese. BMI serves as a useful screening tool to identify potential health risks associated with obesity and helps public health officials track weight trends in populations.

In contrast, measuring water intake focuses on hydration status and does not relate to body composition or fat assessment. The body's oxygen consumption is typically indicative of cardiovascular and respiratory fitness and does not directly reflect body fat levels. The level of physical fitness encompasses various factors, including strength, endurance, flexibility, and body composition, but it is a broader concept compared to BMI, which specifically targets weight relative to height.