I was diagnosed as an adult and I realize there's a significant difference between self-imposed food discipline as an adult and one imposed by parents on a child.
I avoid some foods that make me spike, like cereal. Having said that I had some meatloaf last week made with some breakfast cereal and my post meal blood glucose was well behaved. I did my usual pre-bolus and calculated my insulin dose to cover the added cereal and ketchup.
I also avoid or limit to small portions potatoes, rice, bread, and processed carbs. I do eat berries and also allow some limited addition of table sugar, like sprinkling of berries that are sometimes tart. I also eat meat, fish, eggs, dairy, nuts, seeds, limited amounts of peanut butter, and the less-carby vegetables like broccoli.
Someone mentioned about parents using the "type 1 grit" diet for children as an example of imposing an extreme food discipline and possibly unintentionally setting up an eating disorder. That's a real concern.
Type 1 Grit is a Facebook community dedicated to following Dr. Bernstein's way of eating for diabetes. This method limits carbs to 30 grams per day and distributes them to 6 for breakfast and 12 each for lunch and dinner.
This may seem like an almost impossible discipline, especially when imposed on children. But I've got to tell you that the creativity and energy in this group has identified and posted hundreds of recipes that make living with this protocol possible and enjoyable. It turns out that kids exposed to a wide variety of low carb foods (and treats!) do not feel deprived. I think this protocol can be implemented without the attendant risk of eating disorders if the family is willing to eat this way, too, and if the child has many favored meals to look forward to.
Type 1 Grit is a group that limits membership and I would not encourage parents of T1D children to join without first reading Dr. Bernstein's Diabetes Solutions. This way of eating is not for everyone but don't force yourself into a take-it or leave-it false choice. This method can be adopted in a graduated fashion, something I've done for the last five years. Bernstein's method limits carb grams to 30/day while I have consumed a 50-75 grams/day with great BG success. Carb limiting simply works, an impressive tool to control blood sugar in diabetes.