I have been a type 1 diabetic for almost 40 years. The new insulin Lantus and Novolog does seem to allow me to gain weight more easily but I was able a while back to take off some 25 pounds by staying away from FAT and Lower my Carbs. When sugar went low used quick acting sugar like glucose gel or Coke stayed away from cookies candy bars ect to get it up. Excercise helped not pound wise but did loose inches. Best thing was to eat close to Zero Fat and Low Carbs. Now just and FYI, keep close watch on sugar levels I did have a mishap after leaving a fitness facility due to LOW sugar. I have since put the weight back on but am here looking again to get it off. Good luck to those trying, persistance is the key. Now I need to get motivated.
What you don't say in your post is how you eat? That is what makes you gain weight, not insulin per se! Some Type 1's assume they can eat whatever they want and cover it with insulin. So they take higher doses of insulin and sometimes even have to eat more to match the insulin dose instead of the reverse. Usually Insulin Resistance is a Type II problem but Type 1's who gain weight can also develop resistance which then makes them gain more weight so it is a vicious cycle. Perhaps it would help to talk to a nutritionist about a program of weight loss and lower carbs.