Type 1 can be diagnosed at any age. Of course the younger it is diagnosed the more complications and these complications come sooner. The little ones are the saddest for me to see.
Insulin especially Humalog will put weight on but honestly I think the weight comes because when the bg is high a lot of the calories are sent out in the urine. The hard part is adjusting our intake to a lower calorie amount when we get strict control. We are not use to eating less and now we are using the food calories to our cells where before we were not. So is it the insulin or is it our diet that is at fault in weight gain. Insulin does put on water weight gain.
At times I have to lower in insulin intake for awhile in order to get my body to readjust again. When I then go back to the amount of insulin I need it works better. Many type 1 diabetes know this and do readjust for 3-4 days. If not the units needed would steadily rise. This is of course with type one diabetics on insulin who have had it for many many years. Not for those new to management.
Katy