Well... I can only speak for myself, obv. I'm very slim and don't use any medicine for that. I was medium weight/a bit chubby child, medium adult and then due to various reasons I've gained about 5ish stone.
Lost 7 stone (cal counting, eating healthy), kept it off for the past 10 years. BUT. The food is constant noise in my mind. No, I'm not hungry. I actually don't eat much and I'm ok with that, I'm not starving. But you know how people say 'oh, as soon as you lose weight and become healthier, you reset your appetite and healthy, natural, whole foods become extremely tasty, your tastebuds change'. Well that's total bullshit. At least for me.
I just love processed shit, as simple as that. I must have shit taste, but it's tasty for me, tastier than all those 'wholesome home cooked meals'. If I could, I'd ditch my smoked salmon, avocados, lentils and feta for burgers, kebabs, and LOTS of sugar. Because I love it. I don't do it, because I want to stay slim. But the urge is there constantly.
So it's hard work. Very hard work, actually. I can imagine it might be something similar for other overweight people. I understand them, it's HARD and not everyone can do it.
So yea, eat less, mostly plants, low-ish carb, limit processed food, yadda yadda. Everyone knows that. Fat people know it. The question is HOW. If it would be easy, everyone would be slim.
My brother, for example, is naturally slim/medium. He eats a normal sized meals, likes good 'whole' foods, doesn't like junk food. Doesn't have cravings, so when he sometimes fancies say ice cream or a biscuit, he eats a cone or a few biscuits and stops. I can't do that, I'd demolish the whole packet and go for a second one.