General

Karenjenk:
78.9
which means im 80% fat?
that just seems impossible

ILuvChubbyChix:
No. Body Mass Index, or BMI is a number that doesn't really hold much significance, other than a higher number means you're pretty much heavier.

While rare, a bodybuilder/hardcore gym rat/linebacker/etc. could have an "obese" BMI of 30+ but is probably more fit than most of us.

It doesn't take into account anything like muscle mass, body fat percentage, sex (women in general are always higher), age (tends to rise somewhat with age), bone structure (big boned is actually a thing, but won't explain 100 lbs of difference), or even pregnancy status.

Nevertheless, it's a fun number in the feederism community because surpassing various milestones means you have reached certain goals. 30+ is probably the point where most folks start to look a little heavy, that maybe they aren't exactly thin anymore.