Interesting. Perhaps I missed it, I am not seeing that claim in the link you posted in the comment.
Practically all studies and reviews on the topic emphasize the large individual variability in outcomes. One in six Americans who has ever been overweight or obese loses at least 10 kilograms and keeps it off for at least a year, for example:
https://www.nature.com/articles/ijo201094
That study tracks a sample of adults in the general population, not a group assigned to diet. But evidently a significant fraction of people find success on their own. Most studies on the subject emphasizes substantial individual variability. Furthermore, a strong predictor of long-term weight-loss maintenance is just the initial weight lost:
https://onlinelibrary.wiley.com/doi/full/10.1111/ijcp.12300
https://academic.oup.com/ajcn/article/74/5/579/4737391
and another one is self-monitoring:
https://www.tandfonline.com/doi/full/10.2147/CIA.S25389
In another study, around 30% did not experience significant regain:
https://bpsmedicine.biomedcentral.com/articles/10.1186/s1303...
The notion that "all diets fail" seems to be perpetuated by a few unscrupulous journalists seeking clicks and social media slacktivists doing the same. It's not true, it's not helpful, and it's not defensible.
This is not true and is also potentially harmful if people believe it. In reality, weight regain after "cutting" occurs over a period of years and tends to be around 50%; that is, less than the amount of weight lost in the first place. Several meta-analyses have been conducted, e.g.:
https://www.sciencedirect.com/science/article/pii/S240545772...
It's also worth noting that adults under 60 tend to gain weight over time on average, so the actual effect of the intervention versus no intervention may be underestimated by simply treating the baseline as a constant. Losing ten pounds may seem small, but losing ten pounds instead of gaining ten pounds is more significant.