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Most articles I've read on the matter estimate that between 80-95% of individuals that achieve major weight loss regain most or all of the weight down the road, typically within a couple years. Many people, in fact, will become heavier than they were originally.

It seems that more and more articles are released every week discussing the seemingly "irreversible" metabolic impact of being obese and remaining obese for an extended period of time.

That got me wondering, if the duration of obesity likely impacts long-term (potentially life-long) metabolic function, could the inverse be true as well?

Could there be a critical period of time that a formerly obese person must maintain their weight loss before their normal metabolic function recovers or will they always have "obesity in remission?"

Does anyone know of any long-term studies that address this question?

EDIT (17:30): It just occurred to me, many people that lose large amounts of fat tend to lose a significant amount of lean muscle mass as well. I wonder if this may explain some or most of the loss in metabolism observed in some studies or if that's just a gross oversimplification