These days I usually just try and avoid the issue, or make a joke of it and let the issue get forgotten. If someone persists, insisting I am going to collapse, die, get some kind of electrolyte imbalance or whatever, I usually just say, "look, I am right and you are wrong, give me a few months and we will find out who is right".
However, as time has gone on and I have lost weight and still not pushing up the daisies, most of my friends now just accept it. My family did too, from day 1, because I showed them a youtube video by fastinggurl31. I am please to see this is still available, here it is, http://www.youtube.com/watch?v=CKFR1KcqX9o
I am not tempted by food, so that won't work at all with me. Of course if you are in a close relationship that's different. I would refer them to this forum maybe, or the above youtube video.