First, there is no science shown yet that would indicate someone's insulin sensitivity" would be better just because you are now 14% as opposed to 20%.
You had about 155lbs of lean body mass before.
You now have about 140lbs of lean body mass.
You lost the little muscle you had. That is what regulates your metabolism more...not just a body fat reading.
In short, you cause more damage by losing that much muscle than by being as fat as you were.