I don't think there's any official guidelines posted anywhere. The next best thing I can really do is just share some observations over the years.
I know some might consider categories of pornography, but I would not. Very often, the categories are incorrectly applied.
As far as I can tell, assuming average height (give or take a few inches or centimeters), it seems the defacto minimum is at least 200 lbs, but that I don't often see the term applied to women under about 220.5 lbs or so.
I know, 220.5 sounds oddly arbitrary, until you realize it's not. Or well, it is arbitrary but not oddly arbitrary. You see, 100 kgs is about 220.5 lbs.
So, a longer term goal of exceeding 100 kgs might be a good goal to shoot for.
200 lbs is a nice milestone, which is around 90.8 kgs. But you know, there's also a wonder psychological milestone about 100 kgs, where you cross the barrier into 3 digits, and how you will always need 3 digits to represent that.
This is pretty much just my opinion, but I think it's not too far off of what most folks would probably say.