I’m a T1D and did develop lots of insulin resistance many years ago. My increasing insulin resistance took hold during a five year period when I slowly gained about 20 pounds.
One of the biggest things i learned from that experience is that anyone, no matter their diabetes diagnosis, can develop insulin resistance and that it’s an over-abundance of insulin itself that causes insulin resistance. This high level of insulin can be driven by the home-grown variety as in the case of the earlier phase of T2D or it can result from injecting/infusing too much external insulin as in my case.
I remember correcting high blood sugar with fairly aggressive insulin doses and my glucose level would not budge. It was like I injected water!
I finally made a breakthrough with insulin resistance using a low-carb way of eating. I started with eating less than 50 grams of carbs per day and relaxed that restriction to 100 grams/day for a few years. I now eat less than 30 grams/day.
That eating change led to a 25 pound weight loss and cutting my total daily dose of insulin to less than half what I had been taking.
I know that there are other ways of eating to address this issue but I found enduring success eating a low-carb, high-fat diet. I now eat no processed foods, no grains, and no added sugars. My diet consists of meat, fish, veggies, cheese, heavy cream, yogurt, nuts, seeds, and berries. I limit serving sizes of starchy veggies like legumes or beans.
I don’t think the term, “double diabetes” is helpful in this situation. T1D is auto-immune mediated and T2D is more aligned with straight forward insulin resistance. I did learn, much to my detriment, that insulin resistance can arise in anyone, including people with T1D.
This way of eating allows me to keep my weight in the normal range, feel satiated between meals (I only eat two meals per day.), keep my A1c in the non-diabetic range and reduce my glucose variability as measured by my standard deviation to about 20 mg/dL or 1.1 mmol/L.
This reduction of glucose variability has enhanced my quality of life. It removed much of the metabolic drama associated with swinging blood sugars. I no longer ride the glucose roller coaster like I did when consuming a high-carbohydrate diet.
I know that some people can eat a low-fat, high-carbohydrate diet in a plant-based whole-foods regimen and still benefit from good blood glucose numbers. I think the key take-away from that is that the worse path you can choose, diet-wise, is one that contains both high fat and high carbs, especially processed carbs. This is sometimes referred to as the Standard American Diet or SAD and includes lots of processed foods.
Good luck going forward. Few people like to change the way they eat. It’s akin to changing your political or religious views. It is, however, the most effective lifestyle change I’ve made to improve my health.
I’ve also used fasting as an effective way to increase insulin sensitivity. Even missing one meal helped me. My fasts are usually in the 16-24 hour range.