[jdietrich]

It's an imperfect but useful proxy. It isn't valid as a single number that defines your health, but it correlates very well with obesity. Waist size is probably a more useful metric because of what we've learned about the health implications of visceral fat.

The number of people with a BMI over 30 who aren't obese is extremely small and they're very easy to spot. Arnold Schwarzenegger and Lee Haney won Mr Olympia with BMIs of around 30. Dorian Yates and Ronnie Coleman had off-season BMIs of over 40, but they were the most muscular men in recorded history.

IMO, "BMI is meaningless" is the new "I'm just big boned". The select group of people who really are lean at >30 BMI know that they're a healthy weight, while a much larger group of people are simply using the imperfection of BMI as a means to delude themselves. I'm happy to be corrected, but I haven't heard of a single incident of someone being incorrectly categorised as obese and advised to lose weight by a medical professional simply because of their BMI.