I"m assuming your doctor doesn't have any special concerns because of your other medical problems. If he does, then obviously you need to take those into account. If it's just an issue of him being convinced that people who lose weight at the rate of more than one pound a week are less likely to keep it off, I'd look to see if there is any research evidence to support this. I know it is accepted wisdom -- I've heard this many times myself -- but a lot of the accepted wisdom in the area of weight-loss is not backed up by any data and may well be false.

I think that only you know your body and know how easy it is for you to continue eating this way. For me, personally, I have very few fears that I will be able to maintain this weight loss, because I like eating this way and I slip into maintenance easily whenever I am under stress.

Another way to approach it, if you want a middle ground, might be to experiment with slowing your weight loss down a little. Personally, if I could lose as fast as you do, I think I would be reluctant to slow down, but it's certainly an option. If you want to make your doctor more comfortable, and if slowing to a one pound a week loss would do that, adding a few high calories lowcarb foods (like a couple of ounces of nuts), would probably have that result -- you'd still lose but a little more slowly. As I said, if it were me I doubt I'd go for that, but it is something to consider.

It does seem to me that when you set your mind to doing something, you do it. I think that is probably what will happen to you with maintenance. You will make it a priority and you will maintain, regardless of how quickly or slowly you lost the weight!