>does choosing healthier meal,

For a type 1 diabetic, no (gets more complex with type 2).

Your body produces insulin at a basal rate.

https://en.wikipedia.org/wiki/Basal_rate

If you're healthy between the pancreas and the liver you maintain homeostasis and things are fine.

As a T1D you don't get that base rate, so your blood sugar will mostly trend up and stay high, even without eating anything. You simply have to get more insulin to avoid burning out all the systems in your body and dying slowly.