weight / body fat % clarification

I cannot confirm this but...
The weigh in's have to be staged for the show. Contestants would have to be weighed-in correctly (same time a day, same clothes, barefoot, etc.) for the weights to be considered accurate. I don't personally beleive the lighted stage is an actual scale. Next, the fat% has to be measured with calipers or a water tank. Standing fully clothed on a scale will not measure the fat. My theory is that they show up for a proper weigh in before the filming and the calculations are done prior to that.
I hope this helps.