BMI is not meant as an individual health measure. It's a general population measure valid over a large sample size. 6'4" is a statistically rare height. I beli

BMI is not meant as an individual health measure. It's a general population measure valid over a large sample size. 6'4" is a statistically rare height. I believe BMI is less valid for the extremely tall and extremely short. That doesn't mean it isn't useful when viewing the whole population. For an individual, BMI + a waist measure is a better indicator. Your brother probably isn't overweight, unless he has low muscle mass and a large waist - but that individual anecdote does nothing to argue against the population level validity of BMI.