Healthcare providers use a calculation called BMI (body mass index) to figure whether your child is in a healthy weight range. The number is based on your child's height, weight, sex, and age. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age. If your child is very muscular or athletic, this will be taken into account. This calculation is different from the one used for adults. BMI levels among children and teens are given as percentages compared with other children and teens of the same sex and age.
A single BMI-for-age calculation is not enough to evaluate long-term weight status because your teen's height and weight will change as they grow. With individuals, healthcare providers should consider BMI along with other factors such as family history, blood pressure, blood sugar levels, and eating patterns and physical activity level.