It is my understanding that most weight loss attempts are rather successful at the beginning (several weeks), they tend to slide towards a plateau in a few months and it is a real challenge not to gain the lost weight back in a year or two. Long term success rate seems to be around 20 per cent. [0]

At the risk of sounding stupid or glib, the best strategy is "not to play", e.g. never gain the extra weight in the first place. Which may not be feasible for people who grow up in fat families and already reach adulthood as obese.

But the still-nonobese people should be vigilant.

[0] ... https://pubmed.ncbi.nlm.nih.gov/16002825/