Take pictures!
In photos there was a noticeable difference at 2 weeks for me, but after 50lbs, I still dont see any difference when I look in the mirror but my photos show a HUGE difference.
Other people started to comment after I had lost about 2stone but I think often people dont like to say anything incase they offend you... its like saying "I noticed u were fat... ur not so fat now!" hehe so take some photos of yourself and take another one every month and your see the change in shape, if you look at my diary in the Exante section, there is two pictures of me with only half a stone difference in weight but you can still see my shape has changed slightly (they are towards the end of my diary, the ones on the first post are older pics)