Why don't I think it's realistic....

Because I think of the average sedentary person out there that looks at that show and says "hey if I cut some calories and go to the gym, I can lose 5,8,TEN pounds in a week".
And then they start WW or JC or something, and start going faithfully to the gym, but find it a struggle to lose 2 lbs in a week. So they get frustrated, say "it's too much work" and drop out.

When realistically two pounds is what you should be losing if you are doing it in a healthy manner. And YES it IS a lot of work!!
I can't see how it's healthy for them to be losing weight that fast. But of course that is my opinion, I'm not a doctor.

To be more realistic I'd like to see them show EXACTLY what the contestants do as a daily workout regimen. I hear it's four hours a day, but I don't think I've ever seen it spelled out on the show.
And like you said, four hours a day is not realistic for most people. Even during heavy Ironman training the most I can squeeze in is 1-2 hours in the morning and 1 in the evening, with one long 7+ hour day on the weekends.

I'd also like to see how many calories they are eating, and more of exactly WHAT they are eating. - And not just the blatant product placements.
They did show Kim talking to B about his food journal a couple of weeks ago, but I think they need to go more in depth about it.

Of course you can go on the website and spend $$$ to join "the club", and then I guess you will get the keys to the system..

Personally I would LOVE to go on the show. I love to train, and need to lose a good 20+ lbs. I struggle everyday to get weight off. Now THAT to me is realistic.
Sure, find the fattest people in America, put them on a harsh diet and kill them in the gym everyday, and the weight will melt off.

But the real challenge is to find all the people like me, who have been on one diet or another for what seems like forever. Get our bodies to finally shed the pounds. Now THAT would be a challenge!!