Body Mass Index (BMI) is used to determine whether an adult (20 years and over) is of the desired weight for their height. For children and teens, BMI calculations take into considerations such as their gender and age. BMI has been criticized as an unreliable method because it does not directly measure body fat percentage.
Sean Crawford, (the American 100m and 200m runner) is classified as overweight according to his BMI, even though he is in good physical shape. The limitation with BMI therefore is that it does not differentiate fat from muscle. This is why, to ensure it’s validity, BMI is used in conjunction with other methods such as waist measurements to determine a person’s health.
A BMI under 18.5 for an adult is categorized as underweight, while a BMI of over 24 for an adult is classed as overweight. Please see the table below:
|18.5 – 24.9||Normal|
|25.0 – 29.9||Overweight|
|30.0 and Above||Obese|
In the case of teens and children, BMI is age and sex specific which means that these criteria are taken into account when determining their weight status. BMI’s for teens and children are calculated in reference to other children and teens of a specific age and gender.