alt Hacker NewsIt's still a theory. We definitely don't know the underlying mechanism(s) of action, and it's likely there's more hidden complexity there.
But rapid weight gain after weight loss (until you arrive somewhere near your old weight) is at least a well observed experimental effect. About 80% of people who lose weight, through any means, will revert back to their old weight.
Source:
i lost about 30 lbs a couple of years ago, white knuckling my way through starving myself on a medically supervised diet. within two months of going off the diet, i was back at the exact weight i started at, to the pound, and haven’t varied >2lbs since, no matter what i eat. consider me convinced on the setpoint theory.