After all, Dorian's gut is completely gone now, which shouldn't be the case if he had permanently enlarged intestines.
which means, once again, you really don't know what you're talking about.
if "gh gut" is due to the growth of internal organs, normal catabolic activity would reduce their size over time, but it would take a long time
if "gh gut" is due to intra abdominal fat, fat between the organs withing the abdomen, due to insulin sensitivity, then that could certainly dissipate once you stop using the insulin, but again, it would take a long time