Let's take a look at the Spring 2012 season (the thirteenth overall) of The Biggest Loser on NBC.
Rating the Ratings: A meltdown now more than two years in the making continued for The Biggest Loser this spring, as it took its fifth straight double-digit decline. The show stayed in a tight 2.0 to 2.4 range for each of its 18 episodes, though the show did increase a bit from its late-season 2.0ish level when NBC shrunk the show to an hour to make way for The Voice results show. Sadly, even at these numbers, it was among NBC's biggest shows, but NBC is attempting to move on from their long-running dependence on the show by holding it for midseason in 2012-13. As of now, there's no scheduled timeslot. Grade: D+.
Here's the now updated War of 18-49 post for The Biggest Loser.