"...but it's worth clarifying that BMI is NOT a diagnostic tool."
Bingo.
The BMI was put together out of height-weight tables that were put together by entities (insurance companies and public heath companies looking for funding) that have financial reasons to find the greatest number of people to be overweight.
Sylvester Stallone (5-9, 228 pounds, BMI of 34) and Mel Gibson (5-9, 214 pounds, BMI of 32) are also "obese." So was Mark McGwire (6-5, 250 pounds, BMI of 30) the year he hit 70 home runs. And if politics is your thing, you'll be interested to know that the new governor of California (6-2, 257 pounds, BMI of 33) is obese, too.
Stallone 34
Gibson 32
McGwire 30
Arnold 33