I took care of lots of Type II diabetics back in the day, but not so many Type I diabetics. It's far less common than type II. I'm pretty sure, however, that I never understood: Diabulimia.
Skipping insulin for someone who's insulin dependent can be a great way to lose weight. Of course it can lead to total weight loss (as in death), but that's not quite guaranteed -- at least, not right away.
The article, which is appropriately sympathetic, provides a lot of insight in a quick read.