johnxyz:
Most weight gained is permanent. Fat cells don't disappear, they just shrink. It is the tendency for the cells to return to normal size. I know a lot of 400 pound people who started out planning to stop gaining, and they never could.
Sitsok:
Hmm.... So you 're saying that once you get some fat cells, you can never be thin again?
Well, it's not "impossible", as it's possible to extract the fat cells or destroy them through liposuction or some other deriviative. There's also the appetite for your new diet that will have to be adjusted, either through willpower, or by transplanting a microbiome from a fitter individual to you to stop the cravings from a fatty diet, usually by pill or some other means. Loose skin is also a concern that can be fixed.
Liposuction is getting easier to do these days since some methods require less recovery time, and you can even reinject it as a Brazillian Butt Lift/Cup Up procedure to reshape your growth patterns. But paying for all this? Better start planning your loan or trade up for a job that pays more than $50k/year, because unless people don't need degrees for plastic surgery, make the technology consumer-grade, or find an alternative method, you gonna carry that weight one way or another.
The upside is, if you like exercise and can plan your diet, you can gain a hundred pounds and work it off with none the wiser, but the metabolic damage will stay with you because humans evolved to hoard calories because they never had to worry about being immobile before the renaissance. There's hope in which, if we have mRNA vaccines now, genetic engineers could make cellular profiles which gradually rewrite your body for all sorts of needs, but we are sooooo behind on that kind of discussion.