We don't get America's Biggest Loser here but I've seen the pictures and the controversy.
Firstly, I feel like the poor girl was getting criticised (presumably) for being too fat and now for being too thin - no matter what she does she just isn't good enough for the world. Yes she is a little thin now, I find curvy more aesthetically pleasing, but someone online said she is only 3 lbs under the "normal weight" range, which doesn't seem dangerously unhealthy to me.
Secondly, I've just watched the opening ceremony to the Winter Olympics. Here are several hundred people who have spent months or years on extreme exercise regimes and probably very strict diets, in order to do something a lot more dangerous than standing on a stage. Lots of risk of broken bones and even occasional death. Yet we don't criticise them for getting up at 5am every day to exercise and cutting out junk food, we praise their persistence and commitment. Going for a major goal can be very demanding and not necessarily the best way to be supremely healthy in your old age. But so much better (I think) in all these cases than being obese and doing no physical activity.
And thirdly, I don't know her, I don't know if she has any kind of eating disorder now. But you could just as easily argue that she had an eating disorder before she went on the show, a disordered and unhealthy relationship with food, as evidenced by her obesity. So if she turns out to have some issues now, I don't think they were caused by the show. I think it would be an existing tendency that has turned into a different channel. Like my brother, who has Obsessive Compulsive Disorder, started out with germ phobia and hand washing, and when he managed to supress a lot of that behaviour it burst out again into full-blown hoarding. But the winner was probably just pushing herself hard to make sure she would win.
So those are my three cents worth.