I'll just say look at some gifted athletes who are required by the terms of their employment to stay in top physical condition. For instance Tom Brady. A BMI of more than 27, a "potential health risk".

Or Shaquille O'Neal, with a BMI of over 30. Yao Ming is down there at 27.

BMI measures height and weight, nothing more. It doesn't measure body fat, or muscle mass. It doesn't measure for the relative size of a body's frame, which can seriously differ from a slight frame, to a large frame.

BMI is skewed to favor slight framed humans, and is a global average.

There's a reson why those buoyancy tests are favored by nutritionistas and doctors.

The athletes have a high BMI because muscle weighs more than fat. If you have a lot of muscle and little fat, then your BMI is going to be higher -- even though you are probably quite healthy. I would worry about a BMI of 28 if you don't exercise very much. That would be very unhealthy. But if you run and lift weights, then a BMI of 28 is probably very healthy.

Nice calculator, I have checked it and find my BMI 20.32 which is normal.