Hi and welcome!
Is there a history of T2 in your family, or just T1? I know that there is an increased risk of T1 running in families, but don't think the risks are very high. And not all prediabetics become T2s, so it isn't an automatic diabetes sentence!
Could you tell us a little about your Healthy Diet? Only there is so much mis-information and different ideas around, that what you mean by Healthy may mean something different to me, or others.
There are many different causes of insulin resistance. Being overweight is just one. Drugs can cause it (I am on one of them), also hormone conditions, and lack of exercise. Also a lot of carbs in the diet.
Hope that helps a bit.