The "Biggest Loser" winner, Rachel Frederickson shocked many viewers when she revealed herself during the show's finale Tuesday night, Feb. 4 on NBC. 

Frederickson lost 155 pounds, more than 60 percent of the her body weight.

The former competitive swimmer went from 260 to 105 pounds, putting her body mass index at 17.5.  According to the Center for Disease Control and Prevention (CDC), anything under 18.5 is considered underweight.

Stunned viewers including the show's fitness trainers, Jillian Michaels and Bob Harper seemed surprised to see Frederickson's dramatic weight loss. 

The show's Facebook page received numerous comments of viewers in dismay of what they saw, claiming Frederickson lost too much weight. 

"She and the show cannot possibly think she looks good! She looks emaciated! What a horrible example to young girls and women," Joseph Vanderhoff wrote.

Other comments suggested contestants under weight should be disqualified. 

"Sad you let this happen to Rachel Biggest Loser! You should have a rule that they can't win if they are below a certain weight. Only healthy weights should win. They could have spotted this and helped her. Shame on her trainer and shame on The Biggest Loser," Dusty Dixon wrote. 

Others showed full-on support for Frederickson.  

"I think the controversy over Rachel is ridiculous! Biggest Loser has been nothing but positive and good for lots of people on and off the show. Shut up people and get over it! She is way more healthy at 105 than 260 that's for sure," Cindy Campbell wrote. 

During the finale, Frederickson expressed how she felt about her weight loss journey. "Choosing to own my own path and move forward in this life. Knowing I can take control and do anything, has been amazing," she said. 

According to the Washington State Department of Social and Health Services, people underweight may suffer from certain health risks including iron defiency, bone loss, blood vessel disease, delay wound healing and increase vuneralability to infection.