Again, 1-2 pounds a week is the recommended weight loss for free-range dieters.
Most in house medically supervised diet programs have people losing at a faster rate because it is safe to do that IF and only IF you are monitored by medical peeps on a daily or near daily basis.
I consider the Biggest Loser peeps to be more like the people here in Durham at the Rice Diet center. While in house they have people follow a much tighter diet than when people go out int he world to do the diet free-range. The Rice Diet books all give out the "free-range" recommendations, not the what you do in house diet because most people do not get their vital signs taken every day, or get immediate blood tests when anything starts to look even the least little bit off.
The 1200 calories a day mentioned above is generally a "still safe" calorie intack based on everything I've seen for daily health maintanence. You don't want under that.
I do agree that they use a medically supervised weight loss program because bigger weight loss is more dramatic, but I'm pretty sure they monitor those people closely enough, regularly enough that they are not in danger.
If for no other reason than they couldn't get insurance if they were not being monitored.