Not surprising to me. I watched the show occasionally during the 1st and 2nd season and even I could see it was dangerous.
Even without any diet pills, it was pretty obvious to me that the show was pushing contestants to dangerous levels of dieting bordering on starvation and to extreme levels of physical activity. I’m surprised that there haven’t been any deaths, or many serious back and knee injuries, etc., for that matter- perhaps there were.
And while the contestants did lose an incredible amount of weight and transformed their bodies, some managing to keep it off, most from what I understand gained most of or all of the weight back.
Sure, if one is sequestered away from normal life for months, sort of like being in boot camp, and limited to a highly restricted diet and forced to exercise, sometimes from what I saw on the show, to extreme levels and several times a day, they will lose weight. But continuing that level of effort, without a trainer yelling at them and after the show is over is near impossible.
It is possible for an overweight, even an extremely obese person to lose a lot of weight and keep it off, but it has to be a lifestyle change and one that is sustainable after the cameras stop rolling.