If you're talking about conversation, and because someone asked, all you have to say IMO is you lost over 100 pounds after your last child was born.
For myself, I think it's rude for people to ask how much I've lost. Those who knew me when I was obese might say "Wow, you've lost a lot!" and that's fine, but why do they need to know my numbers? So they can whisper behind my back, "She used to be 50 pounds heavier!"
Besides, I've gained some weight back, so what would I say? And again, who needs to know? Only me!
Jay