NBC has renewed reliable weight-loss hit "The Biggest Loser," solid Friday performer "Who Do You Think You Are?" and winter surprise "The Sing-Off."
 
"Alternative series such as these three bona fide hits are important not only to their loyal audiences but also as strong components of the NBC schedule," states new NBC Entertainment Chairman Bob Greenblatt. "They are each unique, attention-getting shows with terrific producing and talent auspices, and we're proud to be associated with them."
 
All three shows will return for the 2011-2012 season, though the NBC announcement didn't specific how the network will use the shows, which are a two-cycle-per-year staple ("Biggest Loser"), a December event ("The Sing-Off") and a midseason entry ("Who Do You Think You Are?") respectively.
 
"The Biggest Loser" is NBC's top-rated entertainment series among women 18-49 and women 25-54 and, like all of the shows NBC brags about, it performs particularly well in upscale demos. 
 
"The Sing-Off," meanwhile, delivered 25+ percent increases over its first limited run in total viewers and in the 18-49 demographic, airing mostly against holiday-season repeats. It would be surprising if NBC didn't expand the singing talent show beyond its four 2009 airings and five 2010 telecasts.
 
It's a bit harder to explain how "Who Do You Think You Are?" is "a bona fide hit," but certainly the genealogy reality series performs better in the Friday 8 p.m. slot than anything else NBC airs there, averaging 7 million viewers and a 1.4 rating among adults 18-49.