I'm probably over generalising here but....
Insulin resistance happens when someone eats more carbohydrate than their metabolism can cope with. Generally their body then produces more insulin to try to cope with the carbohydrate and the combination of excess insulin plus high blood sugar results in weight gain. So weight gain is the result of the metabolic stress of too many carbs. Unfortunately the weight gain then makes the insulin resistance worse and you are on a vicious circle of increasing blood sugars, insulin and weight.
So, reducing the weight (and increasing exercise) usually helps with the insulin resistance, but the only real cure is to reduce the carbohydrate level to what your body can cope with. This should also reduce the weight. Plenty of folk on here go into remission by reducing their carb intake, but if they go back to the same carbs they were taking before diagnosis they are likely to go back into T2 and insulin resistance and weight gain.
But the amount of carbohydrate that different people can cope with varies dramatically. Some people have to go practically ketogenic to achieve normal blood sugars, others can take what I would consider to be a lot of carbs.