Never got an answer to this before, today it seems to be of more interest. A man with built-up muscles in his arms, shoulders, chest and legs who calculates his BMI will find that he is profoundly fat, maybe even obese. How can a cross-trainer (let alone a body-builder) make use of the BMI with his physically ambitious lifestyle taken into account? Is there a formula of some sort that gym bunnies and (whatever guys at the gym are called) can use that factors in the increased weight of muscle?