I thought (as a simple picture) type 2 is "your pancreas can't keep up with demand because you're insulin resistant" and type 1 is "your pancreas is broken and doesn't make (enough) insulin". So running your pancreas at full throttle while type 2 wears it out and it becomes type 1. There's probably a lot more to it, but I like simple physical pictures to get the initial understanding.

Quilt, as much as 25% of T2 diabetics are T1.5s or LADAs. That's because their doctors didn't bother to test for T1 antibodies, unless they look obviously thin or T1 diabetes run in their family. So some of them are just misdiagnosed and eventually have to go on insulin. (Now, it's also possible for such people to test negative initially and test positive later.) These people's diabetes are driven by autoimmunity, just like T1s, only that they have a longer honeymoon period, and do not start administering insulin while they're juveniles. The issue is not so much insulin resistance (high insulin) as insulin depletion (low C-Peptide and low insulin) for these people. How do these people know? Unless you have a dedicated endo, you won't know: you will know when, overnight, you lose BG control and your fasting is at 200, even though you're ketogenic. Then, you start scratching your head and go to your endo and he tests u and your C-Peptide or Insulin has hit rock bottom.

Obviously, some T2s go on insulin because of the pancreas burn out, as the 70% beta cell decimation upon T2 diagnosis progresses ever closely to 100%. This is a progressive disease, so if you can "stop the progression", as your beloved Dr. Neal Barnard says, you've "reversed diabetes." Also, some T2s go on insulin voluntarily to "preserve their beta cells", not because they're under autoimmune attack but either they can't abide by a low-carb diet or they think pancreas is close to being burnt out.

Now, the open issue is that these are just assumptions. We still do not know whether the so called beta cells are simply dormant or dead. U start reading some emerging research out of Israel and u will realize that it may be possible to "revive" these beta cells that are presumed dead. Or read some research out of UK regarding HCG diet being administered to fledgling T2s, and it may be possible to restore functionality to some beta cells.

My hunch: they're not "dead". It's possible to bring them back. And our BG control is not at the mercy of the depleting pancreatic beta cells. We just don't know how to revive them. Going back to your original query, T2s do not have to become insulin-dependent or T1s. But some T2s were never T2s to begin with. That's the reality of the situation because of the national shortage of endocrinologists and untrained internists treating diabetics.