Hi
@Ruth clarke - and welcome to the forum - I hope you find something useful here...
It all seems pretty complicated, and mainly that's because the more you learn, the more there is to learn, and your history, your gut boime, your genetics, your epigenetics .. all make you unique..
on the flip side of that - you can argue that the majority of the Western World (and by extension) the entire world eventually are headed toward T2DM ... simply because our diets encourage insulin resistance.
.. and immediately you are into "well, what the hell is insulin resistance" - and to be clear, there is a not a great deal of common ground, and it is complicated, so it's difficult to divine what is true from wrong from lie.
But - I think there are two lines that are non-controversial that are worth understanding..
1 - it has been known for centuries that "starches and sugars are fattening" - literally, you can go back to the 1820's and the literature is word for word. The reason is that starches and sugars drive a need for insulin to get the resultant sugar out of your blood, where it's toxic, which leads to...
2 - in the presence of raised insulin and sufficient energy, your fat storage cells will grow. This is a simple summary of medical text relating to how we get bigger at a cellular level. It's simply unavoidable for a lot of people - ironically, "big" people can have less risk of diabetes per se, because they are better able to clear out the sugar.
So - with these two simple pieces of well-agreed knowledge, you can figure the rest out for yourself. A typical diet of carb heavy meals and snacks will have the body in storage mode pretty much constantly - even if you are doing lots of exercise and reducing calories and following the guidelines on staying away from saturated fat and red meat. Especially so, because you have to replace it with .. usually more starches and sugars.
I lost 3 stone over a three year period of religiously scanning and weighing everything, and increasing the amount of exercise and reducing calories, and being hungry all the time, but I had no idea about sugars/starches and insulin, so at the end of that period, at my ideal weight, I was diagnosed diabetic.
The good news though, is that it doesn't need to be hard, and reversing T2DM is possible for a lot of people. Discovering that increasing fats in my diet can lead to better health, as well as loosing weight has been one of the bigger revelations in my adult life.
Whether you are or are not diabetic at any point in time seems critical, but to me is becoming less important - through various strategies, I am reducing the levels of insulin in my body (and I need to be careful here - very low level of insulin is not the goal, but becoming more sensitive to it is..) which over time is making me feel better and better, and in a few months I should be able to be listed as in remission. Already, I have lower blood glucose than most non-diabetic people, but it's all about finding a way to live and eat that brings maximum enjoyment, and the best long-term health; and all of that is a constant journey of learning, and brings in a lot of other important stuff, like learning to be more at peace, and to have better sleep; which is a hell of a short statement ... hell, we could have entire forums about either of those as topics...