I was just wondering if there is anyone out there who has improved their HbA1c levels and /or lost weight WITHOUT using the LCHF method or NEWCASTLE diet.
Yes, for me. I lowered from my HbA1c very considerably during a few months of experimentation using all sorts of methods, with the only common theme being weight loss.
For me (and I can't stress enough "for me") there are two very simple rules of thumb:
1) I need to limit carbs in order to avoid harmful spikes after a single intake of food.
2) I need to limit calories in order to have healthy fasting blood sugar levels.
If my weight increases, my fasting levels increase to dangerous levels. This is regardless of carb levels, e.g. they can be 20g a day or 300g a day. If I'm in a period of weight loss (the important aspect there being my liver is cleared of fat, I think) then my fasting levels decrease, again independent of carbs.
I'd bet real money based on every time I've tested this sort of thing, that I could eat nothing but crisps and cake all day, but so long as I limited calories to say 1,600 and went on a walk tonight, I'd wake up tomorrow with a very healthy fasting blood sugar level, because I am in a period of weight loss.
But I don't eat cake and crisps all day, because the HbA1c is not the only picture. It's been demonstrated in a study that two people can get the same HbA1c, but the one who achieved that by always keeping their blood sugar levels below 7.8 2 hours after a meal by eating sensible, low-carb foods, are much less likely to develop diabetic complications. And that's all that's important really - avoiding the complications.
I can get away with carby foods so long as I go on a walk straight afterwards and I'm well established in a period of losing weight. Right now, calories are my main focus. It's working well and I'm enjoying it. But I'm still very carb conscious. I generally keep them low, and will only consider going higher if say I'm in the hills at the weekends or about to go on a walk in the evening.
You have to find what works for you. Make an honest appraisal of your past behaviour with food, how disciplined you are, how likely you are to give in to binges, what you binge on etc. Based on posts in this forum, the most successful method of weight loss seems to be LCHF. It seems to take some adjustment, then people start to like it, and it often automatically reduces people's appetites. It kills three birds with one stone - keeps carbs low, keeps insulin low to make it easier to burn body fat, and keeps appetite low. That doesn't mean it's right for you, if you haven't found that it reduces your appetite (I didn't) then you will need to calorie count.
With the combination of calorie counting and testing your blood sugars before and after meals, and testing your fasting blood sugar, and weighing yourself to make sure you are losing weight, you won't go far wrong no matter what approach you use.
One thorny issue is the radical reduction of resting metabolism as you lose weight. When you get to your target weight, expect to need to eat a lot less than other people of your size if you don't want to regain weight. The effect may be permanent or at least last for very many years. Short term studies show alternate day fasting minimises the reduction in resting metabolism, but a year-long study says weight loss will be roughly the same as plain calorie restriction.
Other short-term studies show you can restrict calories normally and may stand a chance of keeping your resting metabolism up if you occasionally over-eat (see fourth image in this study, i.e. the first graph):
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018593/
That looks very promising, but then so did the studies on alternate-day fasting. So far, no long-term study says that any one method of weight loss is radically better than another. I think the main thing is we all need to expect a battle if we are to lose weight and keep it off for 10 years.