I am not diabetic but I worked at as a nurse at a diabetes camp all summer and did a lot of research on this (my senior research project is preventing low blood sugars in people with type 1 diabetes while exercising). It is generally known that insulin and weight gain go hand in hand, but I have a feeling that while exercising and eating less carbohydrates your body will need less insulin (obviously).
I don't think your basal rate should prevent weight loss, considering the basal rate is generally low but continuous, and when I spoke with a Medtronic rep/CDE I was told that the basal rate is supposed to mimic the pancreas releasing insulin so non-diabetics would constantly have insulin in their bodies as well. I think the theory is that with blood sugar spikes our bodies release a lot of insulin (in your case when you eat pizza and take 20+ units) which could prevent weight gain. Not positive at all though, I'm trying to understand it as well. I'm thinking though...if this is the case, then would a dual or square wave be better?
A person on injections using Lantus/Levemir would have the same effect because it is long acting, so wouldn't they technincally have insulin in their bodies as well?
Sorry--I had intended to be helpful on this post but I think I just raised more questions...