This is why its imperative that weightloss is treated psychologically as well as physically.
I agree with this.
Firsrly, observations I've made of people who appear to be naturally slim or able to maintain either weightloss or a healthy weight to begin with - they don't overeat and they don't routinely reward or console themselves with food. The food they feel they 'deserve' is food that is nourishing for their bodies and they are mindful of what they consume.
(But I also have to say that, whenever these people post on seeking weightloss advice or "How are you naturally slim?" type threads, they are always shot down with, "Life is too short to not eat cake" and "I love a big bowl of pasta - I suppose that's why I'm a fatty!" type comments. Or people who 'need' chocolate every day. And mocking people who eat a 'massive salad' is a favourite of people on here yet people who eat massive salads generally aren't obese either)
People whose relationship with food is less healthy should receive psychological support to address this if they can't manage it themselves for whatever reason.
If they don't, then old habits will resurface. They're going to however they lose the weight.
People (especially on MN because that's the only place I've read it!) like to say, "Diets don't work." But they do. Of course they do. If you change your eating habits for the better, you will lose weight. If you maintain those good eating habits, you won't regain the weight.
I have no skin in the game regarding WLI. I don't need them, I don't hate them and the people I know who are on them aren't close enough to me for me to know their eating habits (they've just shared it on SM or mentioned in passing that they're on them at work but I don't share meals with them) but it's obvious no one gets to a point where they are prescribed them through eating 'healthily'.
If this were true, we wouldn't see almost everyone who lost weight without medication regaining the weight, which is not the case
Weightloss isn't magic.
If someone is significantly overweight/obese due to poor eating habits and they then return to those same poor eating habits following whatever weightloss strategy they use, it's obvious they're going to put the weight back on.
Maintaining weightloss is possible and I know plenty of people who've done it but it worked because they didn't "go on a diet" as much as they changed their attitude towards food, eating and their diet. Permanently.
But some people want to go back to eating cake, chocolate every day and 'huge bowls' of pasta because that is what they consider to be a normal diet.