Technical explanation - being overweight or obese may cause a fatty liver. In some people (probably due to genetics) a fatty liver becomes insulin resistant, raising fasting BG levels. A fatty liver may also elevate blood triglyceride (fat) levels. Elevated triglycerides may increase the rate at which fat is deposited in other tissues. Fat in such tissues is called 'ectopic' fat - stored in tissue other than adipose tissue (normal fat cells). In some people (probably due to genetics again) high levels of ectopic fat in the pancreas can cause lipid toxicity in pancreatic beta cells leading to cell dedifferentiation. Translation - fat may poison the cells that produce insulin and switch them off, but not kill them. Over time, elevated triglyceride levels may cause this problem to get worse and worse, with more and more beta cells disabled resulting in worsening insulin response.
Solution - lose a mess of weight. This gets fat out of the liver, which may reduce fasting BG levels. This may also lower triglyceride levels. This should reduce the rate at which fat is deposited in the pancreas. Over time, fat levels in that organ may return to normal, healthy levels. As this occurs, a portion of disabled beta cells may 'wake back up', perhaps restoring insulin response somewhat. The maximum immediate benefit is seen perhaps a few months after triglyceride levels come down, though nobody knows exactly how long it takes for all the cells than can wake up to have done so.
It appears that the longer a person waits to get the weight loss done the less effective it is for most people. Roy Taylor (who established how all this might work) suggests that the resilience of a person's beta cells might, again, be genetic. Some people may have 'robust' cells that recover well from lipid toxicity even after a considerable period of time, others not so much. The more robust the cells the more likely they are to 'wake back up' after a period of time. If they don't, the effects of lipid toxicity appear to become permanent in time.
This is basically the reason the remission programme isn't offered to people who were diagnosed many years ago. It would work very well for some people but perhaps not for most. However in your case, you may have already done it. You lost the weight. Bear in mind - I know absolutely nothing, have just been trying to learn as much as I can. Based on what I've learned so far - you may have fat accumulating in your liver again, which you might observe as slowing rising fasting BG levels. If it reaches a critical point you might see elevated triglyceride levels in your blood test results - a bad thing. Solution - if you have weight do lose, lose some more to get fat out of the liver again. If you drink alcohol, cut way down on it.
Alternatively your BG levels might be rising purely due to the effects of aging. For example - we tend to lose muscle mass as we age and exercise less. This, effectively, raises insulin resistance. Muscle tissue is the biggest consumer of glucose in the body. If there's less of it, with a lowered demand for glucose due to less exercise, then there's less places for the glucose in your blood to go after eating. Insulin is less effective, in a sense, as there are fewer and less responsive cells in the body for insulin to act on. Potential solution - try and get as much exercise are you reasonably can. Also, Metformin might possibly help if you're not taking it already.
The remission programme is mostly just a weight-loss programme. With advice from a doctor and/or nutritionist for safety, you could get that done yourself. This document describes the Newcastle Diet approach, which is what the NHS remission programme is loosely based on -
Newcastle Diet PDF. Again though, if taking that approach, do speak to your doctor first as medications might need stopping or very frequent adjustment. Very rapid weight loss is not essential for remission though - any weight loss that is achieved at a reasonably healthy pace will get the liver fat out.
If you do not have significant weight to lose then it may perhaps be time to discuss adjusting medications with your doctor, if you haven't already. Pushing your diabetes back for so many years is a great achievement, one I hope to emulate myself, though none of us are immune to the effects of aging.
Very best of luck!
Edit - typos
