Its not just about diet. You need to do a little exercise. Even if it is just some walking.
Listening to people with the mindset that it is too late in life to change will do you no good.
You will of course also have to acknowledge that some of the foods you love are not good for you, and will have to either cut them right out, or keep them as special treats in your diet plan.
e.g. I have a sweet tooth and love chocolate, but it makes me pile on the pounds. I therefore cut it out.
I still eat sweet things, but mainly fruit.
I can't speak for others, but what I do is make up a big bowl of mixed salad. Cucumber, tomatoes, peppers, carrot, red cabbage, apple, celery and lettuce. This lasts me three or four days. I eat it with some protein: chicken, salmon, steak. Sometimes add a little strong cheddar.
This works for me, but in addition I do exercise. I am ten years younger than you, and try to exercise Monday-Friday.
You can google "Youtube + exercise for the elderly" for lots of videos and advice on that matter.
HTH