Bodybuilders know just how well BMI works for most people because we are outliers.  The work I have had to put in to get to 28.6 BMI with a 32" waist (I'm 6'4") is more than the fatties can even comprehend.  I have a goal of eventually being obese by BMI and underweight by height/waist ratio, gotta gain 20 pounds and lose 2 inches. Further, I'm a LOT bigger than everyone I know (except one guy) and still not obese.  These things act like being obese because swole is easy but even gaining a single pound of pure muscle takes a lot of work.