What the number is
CDC computes adult BMI from height and weight. The About Adult BMI page groups results into underweight, healthy weight, overweight, and obesity ranges for population screening. The page is the source. This lesson does not reprint a calorie target.
What it does not tell
CDC says BMI does not measure body fat directly and does not diagnose health. Muscle, age, and where fat sits can move the number. A clinician reads more than one measure.