I noticed a difference after losing 2 stones. My clothes were looser before that, but I couldn't get into a smaller size yet. Then I tried on a pair of trousers I'd had before that were way too tight, and now they fit, and are getting baggy!
I also have a pair of jeans that I've never worn, a size smaller than what I was wearing, they fit me now, but I still feel they look a little tight yet. I think in the next half stone I'll be wearing them, hurrah!