What method is primarily used to evaluate body composition?

Body mass index (BMI) is primarily used to evaluate body composition because it provides a simple, quick, and widely accepted method for categorizing individuals based on their weight relative to their height. BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters. This measurement helps to identify whether a person falls into underweight, normal weight, overweight, or obese categories, which can give an indication of potential health risks associated with various levels of body fat.

In contrast, bodily surface area (BSA) is more commonly used in medical settings for dosing medications and evaluating physiological parameters rather than measuring body composition. The basal metabolic rate (BMR) estimates the number of calories the body needs at rest to maintain basic physiological functions, making it a measure of energy expenditure rather than body composition. Lastly, the waist-to-hip ratio is useful for assessing fat distribution and associated health risks but does not provide a comprehensive evaluation of total body composition like BMI does. Thus, BMI is the preferred method for general assessments of body composition in a large population context.