The body mass index is a comparison of your weight to your height. A higher BMI number usually correlates to a higher percent of body fat. Although some health professionals only use weight as an indicator to determine a level of healthiness, the Body Mass Index creates a more accurate indicator because it takes into account a person’s height.
The concept behind the BMI is simply the idea that someone who is shorter than average should also have a lower weight than someone who is taller than average. For example, someone who is shorter than average and weighs 70 kilograms will have a higher BMI number than someone half a metre higher, but who also weighs 70 kilograms