Measuring if someone is underweight is usually conducted by measuring the BMI and is determined if your BMI is lower than 20%
Measuring if someone is overweight is like measuring someone who is underweight. It is usually measured by BMI and is determined if your BMI is higher than about 25%
Body Mass Index is measured by the following formula: Weight (kg) / (Height (m))2
Thus, the only answer left that makes sense is A. Energy equation.