I have lost over 20 pounds in the past year and am now a size 14. Recently, I got engaged. I met my chosson several months ago when I was still about an 18. My weight didn’t matter to him then and it doesn’t matter now. (Incidentally, we did not meet through a shadchan). I’m losing weight in order to be healthier and feel better, not to look good for him, although of course I’m happy about that part of it as well.
When I called a gemach to ask about borrowing a gown for my wedding, the woman who runs it told me that she mostly had size 4s and 6s and a very small selection of 12s and 14s. I ended up buying a gown and taking it to a seamstress for tznius alterations (expensive, but what else can you do?)