Fairly self explanatory, it just seems odd to me that the descriptions are the same from 600-1000lbs.
It actually gets really hard to describe things in a meaningful way at that size. I had that problem with my fetishmaster mod. I solved it by finding objects that fit the measurements of the character
Dohavocom basically summed it up. There aren’t very many adjectives in the English language to describe human beings weighing over 600+ because hardly any of said beings exist. Therefore a writer has to be exceptionally creative to “show” the reader just how fat the character is since there aren’t any plain ways of putting it. The challenge we struggle with is to be mindful of a character’s surroundings in events such that NPCs and the environment will interact with you differently according to how heavy your character is. Often times when creating an event we don’t think of the fact that some players may have an immobile blob as the protagonist, or that some players may even have an underweight character, so there might be a disconnect between the character and the environment.
I think it’s a problem with the power curve as well. In real life, major weight gain takes months, plateaus are a thing and due to the square cube law there are limits on maximum girth. It’s hard to mirror that in a game where players expect more immediate gratification. 
I’ve actually found that visual aid helps a writer a lot in this regard. Whether it be someone’s artwork, pictures of people you know, or even just taking a ball and making a quick prop of a bloated stomach, giving yourself something to look at to get reference helps you come up with creative writing descriptions and adjectives. They might not be accurate; an artist’s rendition of a 600+ pound figure might, were it to be implemented in reality, only turn out to be about 400 pounds or maybe much more than 600, but it creates consistency that makes the writing feel better.
And therein is sort of the crux of creatively writing absurd concepts such as characters breaking the boundaries of what is typically considered feasible weight for a human being. Consistency is key. As long as your 400 pound person is consistently described using similar terms and your 600 pound person also described with their own terms, terms which describe them as being significantly bigger than your 400 pound person, you create an internal consistency that is believable even if it isn’t necessarily realistic.