I have nothing good to say about the Biggest Loser. I admire what they're trying to do, but I think that it does nothing good for it's contestants or the people at home watching.
Do you want to know how they lose so much weight?
They starve themselves. Please, go look up interviews with former cast members. Not only have the gained weight back (some have gained ALL of it back), some of them claimed that they remained on fluid diets due to the pressure put on them to lose those huge numbers. This doesn't mean that everyone has done that or that some contestants haven't been successful, but I believe MSNBC did a study about it and found that the Biggest Loser is not a quick fix for weight loss as it claims to be.
Also, they seem intent on humiliating fat people. As if they haven't been humiliated enough! Those silly contests where they have to face their "cravings" and they always have butt loads of cake and other goodies... Because we all know fat people just LOVE cake, right? What a load of crap. There are plenty of fat people who can't stand sweets. What a rude stereotype.
As far as exercise, I also believe that is unhealthy. My friend went to a REAL fitness trainer and he had her start slow so as not to injure herself - ESPECIALLY her knees. And I'm sorry, but Jillian is a b*tch. How can you expect to motivate people by belittling them? You catch more flies with honey, you know? Maybe that's why everyone gains the weight back when they leave the show - the Biggest Loser only taught them how to lose weight while people were shouting in their face, making them exercise 10 hours a day and never eat.
Sorry if I'm coming across as bitter here, but I think the Biggest Loser is just a gimmick. Some people try to GAIN WEIGHT to try out because they get turned away if they're not big enough. This is a reality TV show that's no more "real" than those silly dating shows. It's all about ratings, not about helping people.
EDIT: Here's at least one link with some news on where contestants are now. They try to portray it in a positive light, but their current weight numbers tell a different story in comparison to their final show weight...
Where are the 'Biggest Losers' now? - 'Biggest Loser' on TODAY