I was fat/overweight all my life until I was about 24. I had enough of it and I went from ~94kg to about 85kg quite quickly (through calorie deficit), then over 1-2 years I went to a low of about 72kg. I am about 75-76 now, and have been oscillating in the 72-77 range for the past 5 years or so. It still requires me to be mindful of how much I eat, which has become part of my daily life. I'm not very strict about it, I have days when I eat more and then I compensate by eating less.

I think the mistake people make is they think they can go on a diet temporarily, then go back to the old eating habits and not get fat again. That is nonsense of course, which is why dieting doesn't work. Dieting implies something temporary and you need something permanent.