Now I think you should go and see a nutritionist first to get the correct information, I have listed some suggestions below that I found online but I'm not up to speed on your condition. As for exercising you are never too old to do exercise but if walking is your limit it is still exercising. Definitely find a nutritionist as they should be able to help you with your diet to get the most out of the food you can eat and possible give you more energy.
Eat a balanced diet that includes high-fiber foods, such as whole grains, fruits and vegetables.
Avoid sugary foods and processed simple carbohydrates, such as white bread or white pasta, especially on an empty stomach.
When drinking alcohol, eat food with it.
Eat several small meals and snacks about three hours apart throughout the day.
Exercise on a regular basis
Don't get me wrong, I do thank you for the suggestions.
At the turn of the century, I was told I was prediabetic and had a couple of nutritionists and my doctors and nurses, to eat exactly what you have recommended.
In 2007, an endocrinologist diagnosed a fatty liver, and told me to stop drinking, I had already five years before! He dismissed me as he didn't believe me. He sent me back to my surgery!
My weight had ballooned from twelve stone to sixteen in between.
In 2009, I had symptoms similar to hyperglycaemia and T2. Mainly because of insulin resistance.
I was diagnosed as T2, another nutritionist, more tests, etc.
Same dietary advice. 17 stone.
Went to surgery in 2012, prescription issues.
Had a hypo in front of GP. Referred to another specialist.
My weight was 18 stone.
Series of tests and found to be non diabetic, but having hypoglycaemia.
Must add, I was on my feet all day in work doing a manual job.
My specialist endocrinologist saved my life. First thing was another dietician, more recommendations but cut out the high GI carbs. So I did but kept having hypos but I was losing weight, due to fasting and eating very low carb diet.
It wasn't until I found someone, who had a similar hypoglycaemia condition and advised me to go keto and avoid all carbs!
So I did!
What a difference, my health turned around, lost 6 stone, my general health improved so much, my specialist was impressed. He even agreed reluctantly that my body didn't need carbs of any description.
That is why I say I'm carb intolerant.
You are right, that I need a diet tailored to me. And no one else.
But don't we all?
If you have an imbalance or intolerance, I have had lactose intolerance since very young, I was told to avoid dairy. So it's logical that any intolerance to carbs, find out what they are, avoid and tailor your diet accordingly.
Dieticians follow their training but the training doesn't consider lifestyle, affordability, environment, availability and taste. We are all different, and one size doesn't fit all.
I will even say, that many, many patients have been misdiagnosed and given treatment, drugs and suffered because of these recommendations from the health industry. Most GP's are not trained in the likes of my condition, unaware of the damage they do.
Please do be careful of what you would consider good advice.
Best wishes.