NBC will boost its two-hour season premiere of The Biggest Loser on Tuesday, Sept. 11 (8-10 p.m. ET) with the special Where Are They Now? - a tantalizing hour-long appetizer for broadcast the week before on Tuesday, Sept. 4 (8-9 p.m. ET) in which viewers can catch up with the progress of previous favorite "Loser" contestants.

The announcement was made by Ben Silverman, Co-chairman, NBC Entertainment and NBC Universal Television Studio.

"This is an innovative way to re-introduce an audience favorite and answer the question everyone asks - 'Did they keep the weight off?'" said Silverman. "The series will also kick off with a bang when Jillian makes a surprise return to take on fellow trainers Bob and Kim to help change the lives of what is sure to be our most memorable group of 'Loser' hopefuls yet."

In the fourth season premiere of The Biggest Loser, the contestants will go "back to basics" -- working out at a new location without any of the luxuries of the ranch -- and for the first time ever, a set of twins will be competing, as well as our oldest contestant ever at 62. Returning for the new season are trainers Bob Harper and Kim Lyons with new show host Alison Sweeney (NBC's Days of Our Lives) - along with former "Biggest Loser" trainer Jillian Michaels, who returns in a surprising new twist.

The series' second episode will also be a two-hour on Tuesday, Sept. 18 (8-10 p.m. ET). The series will then air in its regular time period (Tuesdays 8-9 p.m. ET) the following week on Sept. 25.

In the hour-long Where Are They Now? special (Sept. 4, 8-9 p.m. ET), contestants from the first three seasons will return to The Biggest Loser campus for one last weigh-in. Viewers will hear about their struggles -- including how they try to keep the weight off - and learn what has transpired in their lives since their appearances, including surprise "at-home" visits. Additional contestants will also be spotlighted as it paints a realistic picture of how difficult it can be to remain trim -- and how some have gained back weight but hope to shed the pounds again. Over 6,000 pounds have been lost on The Biggest Loser scale to date, and we will find out if that weight has stayed off.

The first reality series where everybody "loses," The Biggest Loser offers severely overweight participants the opportunity to undergo a radical physical makeover without any kind of surgery.

The series challenges and encourages overweight contestants to shed pounds in a safe and recommended manner through comprehensive diet and exercise as they compete for a grand prize of $250,000. The unscripted and life-altering reality series gathers contestants from across the country to face real-life temptations, while being provided with approved weight-loss skills and resources in an effort to help them transform their bodies, health -- and ultimately -- their lives.

"The Biggest Loser" provides the 18 strong-willed, yet hopeful, contestants with challenges, temptations, weigh-ins and eliminations until the final contestant remains to claim the title of "the biggest loser." Each team works out under the supervision of professional trainers.

The series has become a worldwide hit airing in over 75 territories with 25 local productions.

Dont't forget to also check out: The Biggest Loser, Where Are They Now?