The vast majority of people who ask, "How much weight have you lost?" are asking not because they want to know how much you currently weigh, but because they want a chance to say, "Whoaaaa, that's AWESOME!"
And 80 pounds? That definitely deserves a whoaaaa, that's AWESOME!
About a week ago, I overheard some women talking in the changing room at the Y about their weight. They were talking about how much they had to lose, how much time it'd take, how rough it can be--the usual stuff--and one told the other about a friend of hers who'd dropped fifty pounds. "You should see her, she looks like a new person!" I don't know them or the friend they were discussing, but I kind of wanted to hang around and thank them both for actually talking nicely about someone behind her back (I didn't, but I wanted to).
That's the kind of thing people really think about a big weight loss--not what a person has left to lose, but how amazing it is that she's already lost as much as she has. It's a rare person who doesn't know how tough it can be to lose weight; when they see someone who's lost a significant amount of it, they are justifiably impressed.