Hi Megan,
If memory serves, there are 5 causes of insulin resistance: inheritance, dehydration, infection, obesity and high blood sugars.
From experience, I know that the higher my bs gets, the more insulin is required to lower it by 1 mmol/l. What's undeniable is that the more insulin we have floating about, the more resistant we will become to its effects. A totally viscious cycle. So, the first line of attack has to be to reduce the amount of insulin required to keep blood sugars in a normal range.
That's why timo's right, low-carb diets are the most effective means of reducing insulin, blood sugars and, in time obesity too.
All the best,
fergus