What fine observations and a great record. Read the posts of "can do" for a similar record on this site.
For me Diet is the BIG clue. Certainly the insulin resistance diet would be an excellent starting point. The results you have are elegant testimony to that approach.
What interests me is how interlocking the results of an excellent diet are. Whether it be insulin resistance, depleted adrenals, thyroid issues, stressed kidneys or liver etc, in the longer term dietary excellence will do more for the long term rehabilitation of these organs, and a good deal more, than anything else. Very often the results are "whole body" which is what is so rewarding about these changes.