Hi
@Flair
We really cannot answer the question accurately because we can't measure how high or why you have insulin resistance.
I do know that insulin resistance will improve over time doing low carb, higher fat lifestyle. It could be a few weeks or a few months depending on what you eat or don't eat! Your insulin levels will drop according to not triggering the insulin in the first place by eating very low carb.
Until you find your balance through testing and experimentation, you will be only guessing, as I am!
Fasting is really beneficial if you can do it, it helps with the balance of hormones and your body doesn't have to put with digesting all the time, it's akin to sleeping, I feel better after a good sleep, also feel better after a fast. It helps with symptoms.
How you do it, by whatever method you try, is individual, like your diet.
I would suggest doing intermittent fasting and low carb, this works for me.
Best wishes