To be clear, you cannot control Type 1 with diet, at all. Period. People with T1D cannot make insulin, the islets in the pancreas have ceased to produce insulin. At this point in the game, an endocrinologist will probably prescribe shots of a slow acting insulin like Lantus for a basal (background) dosing, and a fast acting insulin like Novolog or Humalog for bolus (meal time) injections. You will have to learn how to count carbohydrates properly. To this day, it's a struggle for me. I like to go out to eat, and don't like processed, packaged foods. Often you are guessing how many carbs are in your meal, and correcting later. Low blood glucose (caused by too much insulin) is far worse than high blood glucose. Push your doctors and insurance to cover an insulin pump. It's easier to do one injection kit every 2-3 days than 4-6 injections per day. That pump, linked to a Continuous Glucose Monitor (CGM) will really help you automate dosing, and get a picture of how his body processes carbs. Speaking of treatments, there is a woman, that had islets made from stem cells placed on her organ sack/membrane that has been making her own insulin. She has not received any insulin injections for at least five years. A cure seems likely within our lifetimes. The procedure requires surgery, but I'd do it in a heartbeat. There's hope.
Yep. I'm in better shape now at 47 than when I was 30. I hike, kayak, skateboard, play drums, and even played in a wood bat/fast pitch league up until a few years ago. Despite being called out in the Americans with Disabilities Act, diabetes isn't always disabling. In fact, T1D seems more manageable than T2D, despite being what everyone calls the "worse version."