There was quite a bit of research in the 1970s which suggested that low carbing could push up insulin resistance. There never was a consensus on why. However, that is why if you are low carbing and are scheduled for a Glucose Tolerance Test, you have to go off the low carb diet for a few days. Otherwise the results will be artificially high.
My insulin resistance turned out to be very high after 15 months of serious low carbing. Since I had not had it tested before, it is unknown whether it had increased after a long stint of low carbing or not. But I am open to the possibility that it might be.
I have twice now low carbed for significant amounts of time (3 years and 15 months) and then suddenly experienced intense physiological burn out. This past time testing revealed extremely high fasting insulin despite a very low carb intake (and a 5.4 hba1c).
Unfortunately, most of the 1970s research is not available on line except for abstracts so the details of the studies can be very tough to track down.
I would not worry about low carbing increasing IR as long as you are feeling good and not running into weight problems. For me the sign of increasing IR was that I started to gain weight at the food intake level where I’d been maintaining for a long time, that I started to feel exhausted all the time, and that I was suddenly feeling hungry all the time with normal blood sugar levels while low carbing. Metformin cleared all these symptoms up even though I ended up eating more, rather than less, carbs with it.
I had cut way back on my Diovan this winter, which may have hastened the process this time since Diovan apparently lowered my insulin resistance. But when I burnt out on low carbing a few years ago after 2.5 years of a tight low carb regimen I wasn’t on any drugs and experienced the identical symptoms.
This seems to be yet another area where it can be a problem for some people and not for others. It is certainly not a reason to avoid low carbing. But if you low carb and start feeling rotten, it’s worth investigation.