Body Mass Index (BMI) indicates what a person's body weight should be according to what?

Body Mass Index (BMI) is a calculation that uses a person's weight and height to assess body composition. Specifically, it provides a numerical value that helps categorize individuals into different weight categories, such as underweight, normal weight, overweight, and obese. The formula for BMI is weight in kilograms divided by the square of height in meters (kg/m²).

The reason height is fundamental to this equation is that it allows for the standardization of body weight relative to body size. Taller individuals naturally weigh more, so height is a crucial factor to determine whether a person's weight is considered healthy for their stature. This relationship helps health professionals evaluate and compare individuals’ weight status across populations, making height a critical component of the BMI assessment.

Age, gender, and activity level are important factors in understanding overall health and fitness but do not directly influence the BMI calculation itself, which is strictly a measurement based on weight and height. Therefore, height is the correct answer because it is integral to how BMI is defined and calculated.