I would not eat fat or protein on the day of the flush. I cannot think of where protein would be present without fat also being present. Any animal flesh contains fat. Not good to eat this on flush days.
I eat oatmeal and a baked potato. It was recently pointed out to me that the oatmeal contains a couple of grams of fat. I think I will still eat that on the flush days, because I have been doing it for over a year and have successful flushes. I eat both things plain.....adding only Sea Salt . No milk on the oatmeal.
Hope this helps.