Thank you, I'm really glad you like it!
I tried to base the early BMI thresholds off my own experiences, but they might be a little too low, so I've bumped them up a tad (in what will be the next update). The new fitness system I've created should help here too as the fitter a girl is, the higher the BMI threshold to the next category.
With the higher weights, you're right, those are likely far too low. Currently immobility kicks in at a BMI of 85, but I'm thinking of raising than to 120 and adding another weight category to fill the gap and help ease the grind.