I think my friends did to start with. I think it shocked them how well I was sticking to the plan. However, they don't now.
I think this is due to a variety of reasons. I've been following the plan side August 2011, although my weight is going up and down a few lbs I had lost over 9 stone at one point (now just under). Just like it has taken me a long time to accept what I've achieved, I think it has taken them a long time to accept it. My friends are nothing but supportive and encouraging now. I think it took them a while to realise this is for good. Whilst I had to adapt to the changes in me physically and mentally, so did they... Confidence, personality etc.
In short I think it takes awhile for people who have known you a long time to accept a big change in your life, because its a big change in theirs too in some bizarre way.
Give people time and it all sinks in!