Which makes sense. The big reason that makes BMI inaccurate is it doesn’t account for muscle mass. Tanks like Halfthor Bjornson, Brian Shaw, or Eddie Hall are all gonna be mislabeled as obese, when really they’re just 75% muscle.
Kids however, almost never have a lot of muscle mass (it can actually be detrimental to their growth plates if they were too muscular). So that problem doesn’t show up for them.Honestly, it’s fine for adults as well. Anyone with a muscle mass that would make it invalid would know that.
A proper BMI actually does account for muscle mass by determining how much fat you have on various parts of your body, typically measured with calipers or similar.
Had an instructor demonstrate how two guys roughly the same height and general physcal size had different BMIs where one was around 16% body fat and the other 25%
TL;DR height and weight to calculate BMI is just as inaccurate as someone taking your pulse for 6 seconds to determine your blood pressure.
