"In reality, because of the obligatory homeostatic counter-regulation that occurs with weight loss, to sustain this degree of weight loss, patients would need to maintain a diet that is generally well over 500 KCal less than they started out with. Always remember, that many of the successful weight-loss maintainers of the National Weight Control Registry are surviving on 1200-1400 KCal per day! (not very different from the effective caloric intake of a post-bariatric surgery patient)."
I don't feel much like writing tonight, but wanted to answer your question, so have supplied what I feel are excellent sources of info. Do not be discouraged, but DO be realistic, as it sounds like you are. It is my belief that over time, and I mean years, some healing can occur. I personally believe that this takes alot of careful experimentation and optimizing and highly consistent clean, paleo, and in your case, as a low carber, continued low carb eating.
Are you taking any supplements? I fall on the side of the argument that those who are or have been obese need consistent, high quality supplementation. In your case, I'd recommend a baseline of something like GNC's UltraMega Gold for men over 50 or very active men. I would also suggest additional zinc and magnesium in the form of mag citrate or gycinate, probably 400mg/day. Citrate will help move stool if that is an issue for you. As well, for many, it is calming and induces sleepiness if sleep is an issue. Vitamin D at 5,000/day and then get your level checked in 3 months. The GNC is quite comprehensive except for the amounts of the above cited. However, I do believe they have increased their D to 1800 now, so figure that into the amount of D you take.
I also would recommend a high quality Omega3 at 2-3GMs, like Barleans brand or Carlsons. Studies are not conclusive, but there has been good research showing a thermogenic effect as well as the other positive effects you may be aware of re: joints, anxiety/mood, heart, eye, etc. If you like cold water fish, that would obviously be a good thing to eat for 2-3 meals/week. CQ10 200mg/day would be good to consider, especially in light of your illness history and meds you might have been taking. I also take a slow releaseVit C 1000mg/day.
The youtube talk ^^^ by Steve Phinney, MD is excellent. If you don't have his book, The Art and Science of Low Carb Living, buy it!!!!
There are a number of good and some excellent big weight loss maintainers blogs on the net. Barbara Berkeley's: Refuse to Regain is an excellent physician blog with a wide audience of maintainers.
My very favorite is: Debra's Just Maintaining. It is now not active as she has gone on to other pursuits, but is really of extraordinary high quality and has lots of high quality science as well. It is a difficult blog for some people because the truth of big weight loss maintenance is a fairly harsh and well kept secret, but if you can glide past the angry tone in some posts, it is really worth reading, practically in its entirety.
My own history is that I am a 58 year old female low carber who "clean" low carbed 99=02.I was 240lbs and lost to 145-148 originally and have been maintaining that approx90lb loss since 02. I stumbled into "paleo" in late 09 or early 10. I have lost additional weight over the last approx 1.5 years and am now 130-132 at 5'6".
You didn't mention any exercise?
Sorry this has been a sort of chaotic/ramble, but I am mentally tired tonight!
Hang in there. There are other low carb maintainers here who have lost and maintain large amounts of weight. Their experience can be helpful to you!