I seem to recall in the dim and distant past having my body fat tested at IOT Cranwell with calipers well before BMI became trendy. In those days they still had height/weight charts and limits for aircrew/non-aircrew regarding weight. If I recall correctly aircrew had to be within 10% of their ideal weight and others within 25%. Body fat was measured but not taken into account - I think it was just done to emphasise how much fat we lost during IOT. There is no reason that the quacks cannot use body fat percentage; it would just mean buying an appropriate scale from Argos! The general consensus is that BMI is not a good indicator for anyone of an athletic nature.