I lost 7.5 stone in about 6-7 months 8 years ago. Kept it off and lost slightly more since then, BMI 19 now. Went from 110kg to 63kg originally. That's 17-and-a-bit stone to 9.9, I believe.
The single and only reason which enabled me to do this was because one day something in my mind just clicked. I was deluding myself until that point, thinking 'it's not so bad, I'm not so fat, etc'. In reality it was horrid, I looked shit and couldn't even climb stairs without getting breathless. After that 'click' it was easy, that 'click' was the most important thing for me.
Ok, so I obvs didn't do it 'healthily', but you did ask. So I ate one meal a day, no more than 800 kcal/day, some days 600. No sugar/sweet shit, low-ish carb, low fat. Mostly piles of veg, some lean meat/fish and pulses/legumes. I did, however, drink alcohol occasionally. Weighted everything and logged everything (my fitnesspal) religiously. If I needed to make a meal, I measured and weighted every ingredient separately, including cucumbers and the like. No cheat days during those months, except twice: Christmas and my birthday.
I was hungry at first, but then my stomach shrank and it was ok. I didn't do any exercise except for normal every day activities and walking. I was young, so my skin just sprung back quite nicely.
Ozempic wasn't available then, I didn't do shakes, as too expensive and I need to 'chew' something to feel satisfied. I don't smoke (no appetite suppressant)
So yea, went from size 18/20 (I'm 5'11'') to an 8. After my diet I calculated my TDEE, upped my cals to that, and kept the weight of for the past 8 years. Put on a bit during lockdowns, but lost it again.
I eat healthy, meat/fish, lots of veg, some fruit, some dairy, legumes/pulses, etc. Some pasta, some potatoes, etc. Still no added sugar, though. I drink alcohol (not every day, obvs).
My health is fine, I feel great and look good in whatever I put on. I'm happy.