> Many active gym people have pretty high BMIs but fairly low fat (because muscle is dense),

I’ve been in the overweight BMI category with low body fat by being active at the gym and focusing on diet. It takes some work to get there.

If I check the calculators for the obese BMI range, there was no way I could get there without either gaining a lot of fat on top of the muscle. The amount of muscle required to have an obese BMI with healthy amount of fat is absurd.