It will be radically different for this doctor to have a patient that is improving, rather than sliding down that ramp to deaths door. You will be the patient he enjoys seeing walk through the door.
I just want to reinforce this, having just got back a few minutes ago from a medical visit in which:
1) My doctor came through the door into the examining room with a spring in his step and asked "How have you been?" with genuine enthusiasm, curiosity, and keen interest -- a dramatic change from the low-affect professional inquiry when I first started seeing him as a +500lb diabetic with high blood pressure and cardiac concerns.
2) My doctor was impressed by my loss of 15 pounds in two months over the holidays, and astonished when he took note of the fact that I lost 134 lbs from Christmas to Christmas;
3) My doctor confessed to me "I was concerned for your life when I first started seeing you..."
4) My doctor expressed interest in my diet for the first time, asking me "what exactly are you eating, anyway?" and expressing concern about my protein sources (LOL) until he found out I was eating lots of beans;
5) My doctor told me "You're doing what I wish all of my diabetic patients would do" -- despite the fact, which I tactfully avoided pointing out to him, that he never suggested anything of the sort; and
6) My doctor followed me out of the exam room and down the hall as I left, pointing me out to three different people who work in that little clinic and saying "He's lost 134 pounds in the last year, isn't that great?"
All in all, my impression was very much as Jim suggested: a doctor who was learning something from me, or if not that, at least a doctor who was enjoying the experience of having a patient unexpectedly get better instead of (inevitably, in his experience and expectations) worse.