Oh sorry I'm not arguing that it never happens, just that in every clinical trial I've seen that followed participants for 5 years it was so rare to keep the weight off that the average weight loss for the group was insignificant(clinically not statistically).

That’s probably the same effect as with Weight Watchers where long time success is rather limited. I have been there too. After couple years old habits return, one starts eating bad things, something happens (let’s take some illness) and exercising ends. Pounds are coming back and cycle starts again.