Also, you have to remember that the primary reason for the show is entertainment, not helping people. We'd probably be shocked at the release releases they are required to sign. I'm sure they sign away any right to sue the show if they would get injured or become ill or even die because of what they are expected to do on the show. Doctors are also standing by, and probably an ambulance is on site as well (at least I would hope so - my dad was an EMT and all of the local marathons and bicycle races always had an ambulance on site and those were healthy, fit people for the most part).

At the size some of the contestants are, they're at risk for stress fractures and other injuries and health problems such as gallstones from the exercise and crash dieting. But you don't see any of that.

The show says "don't try this at home," (in small print at the end of the show), but doesn't explain any of the risks, which I think does imply and even encourage "play along at home." The problem is at home, you're not supervised by a large medical staff.