Rachel Frederickson, 24, of Los Angeles won the Season 15 title of "The Biggest Loser" and the $250,000 grand prize, but promptly sparked criticism from viewers who say the show went too far by allowing the former competitive swimmer to diet her way down to 105 pounds.

Frederickson started the competition at 260 pounds and lost 155 pounds, or 59.62% of her body weight.

When the voice-over artist first walked on stage at the finale of NBC's reality weight-loss TV show, she did so to oohs and ahhs. She was wearing a diaphanous silver dress that skimmed her new figure and all but signaled that victory would soon be hers.

PHOTOS: Rachel Frederickson at 'The Biggest Loser' finale

But as she came into sharper view, it was clear that Frederickson was dramatically thinner than the last time viewers saw her, winning "The Biggest Loser" triathlon.

The cameras turned to trainers Bob Harper and Jillian Michael, who seemed to be clapping in slow motion as they looked her over, their eyes appearing to reflect surprise at her appearance. (See the third image in the photo gallery above, a TV screen grab that is making the rounds on social media.)

Frederickson came into the show with a heartbreaking backstory. She was a competitive high school swimmer who gave up a full college scholarship to follow her boyfriend to Europe. The relationship ended, and Frederickson came home full of regrets and ate to tamp down her sorrows.

PHOTOS: 'Biggest Loser' Season 15 before and after

She said she gained more than 100 pounds and had trouble recognizing herself in the mirror.

Earlier in the season, Frederickson said that winning the show would allow her to reclaim the champion within and embrace an empowered new future. Week after week in the weight-loss competition, she proved what a fierce competitor she was and was all but destined for a spot in the finale.

Frederickson is slated to speak to the media Wednesday morning during a conference call, and will no doubt be asked about her weight.

Regardless, the finale is sure to add fuel to the show's critics who question the safety of the measures it uses and the ethics of grueling weight-loss regimens as entertainment.

In the meantime, many viewers have taken to Twitter to express their fears that Frederickson has become too thin, and to call on the show and the network to address concerns that the weight loss was too extreme:




Not everyone agreed, however, as some social media pundits noted that Frederickson was in it to win the game and will now be able to put a little weight back on, as many past contestants have done. Still others praised her transformation.

Debate over Frederickson's appearance seems to have overshadowed -- at least for the moment -- the stellar transformations of many of the other competitors, including "American Idol" winner Ruben Studdard, who took to the stage to show off his sleek new physique and his new single. (He lost 119 pounds, or 25.76% of his body weight.)

Other top performers included David Brown and Bobby Saleem, the two finalists vying with Frederickson for the top prize. They lost 54.28% and 52.51% of their body weight, respectively, far less than Frederickson. The winner of the at-home prize was Tumi Oguntala, 41, of New York, who started the show at 319 pounds and lost 175 pounds, or 54.86% of her body weight, to end the show at 144 pounds.

As you look through the photos above, what do you think? Tweet me @ReneLynch

ALSO:

PHOTOS: 'The Biggest Loser' finale

PHOTOS: 'The Biggest Loser' before and after

Jay Leno's top joke targets were Bill Clinton and O.J. Simpson