What researchers found years later
Follow-up research on contestants from the reality show found suppressed resting metabolic rates that persisted for years after the competition ended -- in some cases even lower than would be predicted purely from their new, often higher, body weight after regain.
Why this happened
The extreme rate and scale of weight loss on the show -- often dozens of pounds over a matter of weeks -- is thought to have driven an unusually large and durable adaptive thermogenesis response, beyond what's typically seen in more gradual weight loss.
The lesson for typical dieters
This doesn't mean any weight loss causes permanent metabolic damage -- more moderate, gradual approaches don't show effects of this magnitude in the research. It does suggest that faster and more extreme is not automatically better, and that the body's adaptive response scales with how aggressively it's pushed.
What "moderate" looks like by comparison
Health organizations commonly cite 1-2 lb per week as a sustainable pace for most adults -- a rate associated with far less dramatic metabolic adaptation than the multi-pound-per-week losses seen on extreme competition-style programs.