NBC has announced it has renewed The Biggest Loser for a fifth season and also revealed a new twist that will be facing contestants participating in the weight-loss reality competition series' upcoming installment.

For the first time in the show's history, The Biggest Loser's fifth-season contestants will compete while paired in teams with somebody they have a pre-existing relationship with (such as a family member, friend or coworker).

"For the last four seasons, The Biggest Loser has taken on the fat that has plagued America for decades," said executive producer JD Roth. "Our scale has been there, and will continue to be there telling these inspiring stories of weight loss for years to come."

Production on The Biggest Loser 5 is scheduled to begin this fall, and the show's NBC spokeswoman told Reality TV World it "may" air as a mid-season replacement sometime early next year. 

If the show's fifth season were to debut in mid-season, it would represent the first time NBC has aired two regular The Biggest Loser seasons in the same television season.  All four of the The Biggest Loser's four previous editions -- including The Biggest Loser 4, which premiered earlier this month -- have aired as part of NBC's fall schedule.  (The only exception was The Biggest Loser Special Edition, a spinoff that aired a six-episode run in January and February 2006.)

"The success of The Biggest Loser brand continues to positively impact viewers and participants worldwide," said executive producer Mark Koops.  "Having a fifth season pick-up is fantastic and knowing the show will be able to further promote a healthier lifestyle is the best reward."

The Biggest Loser's fourth-season premiere broadcast on September 11 averaged 7.8 million total viewers as well as a 3.1/9 rating/share in the Adults 18-49 demographic.  Its second episode last week improved in both areas, averaging 7.9 million total viewers and scoring a 3.4/9 rating/share among Adults 18-49.

"The Biggest Loser continues to be a top performer and important franchise for NBC, and season four is already off to a great start," said Craig Plestis, NBC's executive vice president of alternative programming. "We look forward to the fifth cycle of the show, and continuing to entertain and inspire viewers all over the country as they watch these remarkable contestants achieve life-changing results."

New fourth-season host Alison Sweeney will return to helm The Biggest Loser's fifth edition.