If You're Not Happy With Your BMI . . .

. . . you should enjoy this article from Slate, which explains why body mass index isn't a useful or terribly meaningful statistic:

BMI simply doesn't work when it comes to individual measurements. Whether that's a problem worth worrying about is another question. Some researchers say BMI's inaccuracies in individual measurements result in little actual harm, since an attentive doctor can spot outliers and adjust her diagnosis accordingly. But this begs the question: If a doctor's eye is better than BMI at determining a patient's healthy weight, then why use BMI for individuals at all?

The article also reveals the history of the BMI statistic. It turns out that body mass index was the creation of Belgian statistician Adolphe Quetelet (who, as it were, had no significant medical training or experience).