one measure is abdominal girth and belly fat. if you've got a lot of fat around your middle, this portends very poorly for your health. i don't think there's any use in ridiculing the obese or making them feel like they are second class citizens, but to pretend that this can in any way be healthy is a big disservice. rather, obesity needs to be looked at for what it is, a health issue. there is enormous cost to this in terms of healthcare. who will pay for it?
i think there are limits to how much muscle you can have and be healthy. i was around 235 and 5'10" and not "fat", because i worked out constantly in the gym and ate even more constantly to hold that weight. was i healthy? not at all. now i'm at 210. i'm trying to break myself down and get to 180 lbs, maybe even 170 lbs. carrying so much weight is hard on your organs, even if it is mostly muscle. thin people with good health habits are the healthiest, so while i'm not a strictly going by bmi, i think bmi is still an important indicator.