It's about more than controlling weight and dieting - being fit and healthy is paramount.
To keep weight off, especially as we age, we need a diet that is sustainable. Many have found cutting out or at least reducing UPF, refined carbs and sugar (as well as alcohol) are key.
So, lots of vegetables, moderate amounts of lean protein, small quantities of complex carbs, healthy fats/nuts, fruit and dairy/Greek yoghurt. After a while it becomes a way of life and I no longer need to count calories.
Lots of books and YouTube videos on this, but I particularly like The Sugar Solution by Dr Mark Hyman and Dr Becky Gillaspy's short videos.
However, the older we get, the more important it is to preserve fitness and muscles. Focusing on resistance/weight based training has made a tremendous difference to my fitness.
I'm 70 and fitter than most women in their 40s. And I absolutely love working out with my dumbbells - thanks to Caroline Girvan whose programmes are excellent. Started out with 3kg dumbbells, now using up to 12kg. I also do a fair bit of cardio (Growingannanas), plus yoga-type stretching in the evening (Yoga with Kassandra).
Personally I find working out both motivating and energising. Plus I'm less likely to eat crap if I've spent an hour exercising.