So, I noticed the tags for fat don't line up with real world values. The following are calculated for a 5'9" male.
For slightly_chubby, it's below 200 lbs, which would mean it correlates with a BMI of 25-30, which would be overweight.
For overweight, it's 200-300 lbs, which would mean it correlates with a BMI of 30-40+, which would be obese
For obese, it's 275-385 lbs, which would correlate with a BMI of 40-55, which would be morbidly obese
Finally, for morbidly obese, it's 385+ lbs, which would correlate to a BMI of 60+, which would be "super-super morbidly obese"
It isn't that big of an issue, but it is misleading/confusing.
(the fact that e621 is owned by an American company is not lost on me, lul)