I'm not sure exactly if I understand your question. If I wake up at 85 and don't eat till dinner, for example, my BG will generally go sideways within say 70 to 100 band. There will be exceptions to this but it will not usually climb or dive steeply. If I exercise, I will have to eat a small snack without an insulin dose or do a minus 20% basal rate starting one hour before I walk. If my exercise is more vigorous, I'd have to compensate more.
It generally won't rise if I'm inactive, such as reading on the computer. This being the wily and devious diabetes, there are exceptions! Like if my infusion site is in its third day and starting to get tender and a bit stale, my BG could start to rise.
My basal rate, without adding any food, will usually keep me within a 20-30 mg/dl window. That's common for me but I do have my days when things don't remain stable. It's a dynamic game. Just when I think I have things figured out, it changes.
Did I answer the question you had in mind?