BMI is a crock. It's supposed to be a standard to measure how fit you are, but the problem is, the fitter you are, the more it's off by, which is insane.
If you lift weights, and you tend to carry more muscle than what the BMI states to be the "average", you are screwed. That's part of the reason why some insurance companies are created especially for athletes. If these athletes tried to get insurance through a regular insurance company, a BMI would put them at obese, whereas an insurance company that caters to athletes and athletic types will use other more realistic measurements to determine fitness (such as water displacement and skinfold tests).
Koffee