I've gone through the drill of losing weight by dieting, then gradually putting it back on again a few times.
I'm in my late 60s now. In my early 60s I was overweight by about 20 pounds. In my last go at it, I lost the weight slowly over a period of years, and I've kept it off for a couple of years now, without ever 'suffering' (much). Mostly all I did was think before I ate something, asking myself do I really want this food? Since my metabolism has apparently slowed down, I can't go by old habits. I've learned not to eat meals at night, just something very light (some nuts, or a slice of toast with olive oil, something like that) at night if I'm really bothered by an empty stomach.
I don't know what's different this time that I'm keeping it off, except maybe practice makes perfect. Also, I'm old enough now that I get serious feedback (backpain, hard to sleep at night, sciatica) if I don't take care of myself. I see other people my age who are out of shape and I don't know how they can stand it. Maybe they are actually tougher than me intrinsically and that's why they can endure it. I don't consider it to be a question of will power or character on my part.