That also makes it slower to change size
. If, for example, you carry a lot of your weight
on your waste, you may drop through sizes faster than some one whose weight is more evenly distributed.
I've observed that sizes run bigger now than they were several years ago. So I don't know if the size I was when I was underweight would translate to today's sizes.
Anyway, you don't know what you body would look like in that dress.