Just echoing what others have said about BMI. It really isn't the best measure of how healthy you are or aren't. It's a statistical measure meant to be applied to large populations, not to analyze individuals.

In my case, I recently had a DEXA scan to measure my body composition. From that I learned that, assuming no loss of lean body mass, even getting down to 18% body fat (in the "Athletic" range for women by most measures), I would still be categorized as Obese. I wouldn't get myself out of that category until getting down to 13.5% body fat, dipping close to the Essential Fat level and probably not very sustainable/comfortably livable. Even then, my BMI would still be 29.8...so just barely out of BMI's Obese category.

I'm not suggesting that my situation is the norm (at all). I realize that I'm something of an anomaly--with my big bones, big muscles and average height (just under 5'5"). I'm just pointing out that BMI is not the end-all be-all of body measurement or analysis.