It’s well established that BMI doesn’t work well for diagnosing individuals but is a reliable and valid method for measuring obesity in populations. For individuals measuring body fat percentage is probably the most accurate measurement, but given the cost of reliable body fat percentage measurements, a scale, a mirror, and some honesty is what a person really needs.

I’m unsure I ever meet an adult that was obese on the BMI, was not obese by body fat percentage scale, and did not know BMI was inaccurate for them.

[0] CDC: BMI is not a valid diagnosis tool, but is generally correlated with body fat percentages. https://www.cdc.gov/obesity/downloads/bmiforpactitioners.pdf