Why is the BMI chart inaccurate

BMI child

Basically, the calculation of the body mass index for a child is the same as for an adult. Only the meaning of the value varies.

BMI calculator child

Note: Our computer is designed for use on the desktop.
A research team (K. Kromeyer-Hauschild, M. Wabitsch, D. Kunze et al.) Published studies in 2001 in which a large number of boys and girls were measured. This results in diagrams with the distribution of the body mass index based on age.

In the diagrams, the value calculated above is shown as a dark red line. So you can easily see where your child's BMI is.

BMI boys

BMI girls

The diagrams show the age horizontally from left to right and the body mass index vertically from bottom to top.

You can see so-called percentile curves in the diagrams. These indicate the distribution. For example, P50 means that 50% of children have a higher and 50% a lower BMI. P3 means that 3% of children have a lower BMI.

Overweight is defined from P90. So the 10% of children with the highest BMI are considered overweight. Underweight is defined under P3. So the 3% of children with the lowest BMI are considered underweight. In the tables above, the two areas are shown in gray and the normal weight area between them is green. It is unclear why these percentages were chosen. Probably because the values ‚Äč‚Äčthen fit well with those of the WHO BMI table, which apply to adults. It is more a statistical assignment than a medical evaluation. Since the body mass index is extremely inaccurate anyway, it no longer plays a role.

A classification in this form can be viewed very critically, especially with smaller children. A small growth spurt is enough to reduce the BMI significantly. A child should therefore never be put on a diet just because you think the Body Mass Index value is too high. Be sure to talk to your pediatrician beforehand.