So then IYO what causes type 2 diabetes, and how do you avoid it? If you already have it, are there natural ways to control it?
The etiology of diabetes mellitus (all types) is generally unclear.
Type 1 is characterized by a complete or nearly-complete destruction of the body's pancreatic beta cells (somewhat simplified, these are responsible for the production of insulin). It appears to be an autoimmune disorder. It generally manifests during youth or adolescence and seems to be predominantly genetically driven, although which genes are involved and what triggers them remains, again, unclear. It always requires exogenous insulin to control the patient's serum glucose levels.
The etiology of Type 2 is even more unclear, and Type 2 diabetics can essentially move into the Type 1 category if they lose all (or most of) their beta cells. This can happen after years of uncontrolled high blood sugars, which in and of itself is toxic to beta cells. Type 2 diabetics may have a normal or close-to-normal number of beta cells and still produce insulin. But the production is often insufficient and/or poorly regulated. They may have an inadequate first phase response but stronger second phase or less commonly poor basal regulation, or they may exhibit dysfuntional hepatic glucose production. On top of that they often exhibit very high cellular insulin resistance (i.e., insulin they produce is not adequately taken up and used by their (mostly muscle) cells).
The causative factors for Type 2 diabetes mellitus are completely speculative. A good guess might be that there is a strong genetic component that requires one or more environmental factors to be triggered (i.e., both the genetic and environmental factors are necessary, but likely none alone is sufficient, to manifest the disease). But these are only guesses and much clinical research remains to be done.
The sine qua non for diabetics, Type 1 and Type 2, and pre-diabetics (i.e., mild diabetes), is to normalize blood sugars. The goal is to have the same serum glucose levels as those with naturally truly normal blood sugars. Consistently elevated blood sugars over many years, even those classified as pre-diabetic, cause serious complications and lead to increased morbidity and mortality.
At least for now (although research continues) diabetes cannot be cured. But blood sugars can be controlled so that one can live a full life free of the complications of the disease.
For solid information about high blood sugars and how to normalize them, I highly recommend the book "Diabetes Solution" by Dr. Richard Bernstein. It explains how everyone, including pre-diabetics and diabetics, can and should have normal blood sugars. The protocol (highly simplified) laid out therein for achieving truly normal blood sugars in a nutshell is as follows (note that each step includes all the previous ones, i.e., if #1 isn’t enough, you add #2, if still not enough you add #3, etc.):
1. First and foremost, a low-carb diet. No one with blood sugar control issues can achieve truly normal blood sugars without it, no matter what medications they're on. Dr. Bernstein's diet calls for less than 30 grams of carbohydrate per day for average-sized adults. I try to adhere to that, but it is pretty tough and may not be necessary for everyone. If your blood sugar control is only marginally compromised, you might first try below 100 grams per day. If that's not enough, try going down to 50 grams per day, then 30.
2. If diet alone is insufficient to achieve normal blood sugars, add exercise, both resistance and cardio.
3. If still insufficient, add oral agents. Metformin first and foremost. If that doesn't work, there are others and other combinations to try.
4. If still insufficient, add insulin.
As for how to avoid diabetes, there simply is no clinical evidence. If you have a strong genetic pre-disposition to diabetes it is likely inevitable. Conversely, for those whose genes guarantee them absolutely normal blood sugars throughout life (a fairly significant percentage of the population) there is no need to do anything (although there are other reasons besides avoiding diabetes for adopting good health habits). For those in the middle, e.g., you haven't been diagnosed as diabetic but you have one or more diagnosed diabetics in your immediate family and you have a tendency to chubbiness and you've had slightly elevated fasting glucose tests (several over 95), I would suggest trying to follow a low-carb diet, take regular cardiovascular and resistance exercise, and have an initial Oral Glucose Tolerance Test (see
Glucose tolerance test - Mayo Clinic) and follow up every year or two (you can try this at home if you want an approximation of the OGTT:
https://bit.ly/2Iixe87, although it's not as definitive). I'm afraid that's all medical science has to offer at this time.