Former “Biggest Loser” contestant Ruben Studdard congratulated Rachel Frederickson after she won the $250,000 prize from the hit NBC show. Her win, however, has been filled with scrutiny after some said that she reached an unhealthy weight. While the celebrity judges from the hit show have refused to directly comment about her 155-pound weight-loss journey -- she went from a size 22 to a 0/2 -- Studdard is speaking out.

"The one thing I will say about my friend Rachel Frederickson is that she is a hard worker," Studdard told Extra's Maria Menounos. "I've never seen anyone work harder to change their life than Rachel."

"'The Biggest Loser’ is about making changes in your life, and she has most definitely done that," Studdard said about Frederickson, who was 260 pounds when she entered the competition. "This young lady was a champion swimmer, a six-time state champion swimmer, and she had a lot of setbacks that made her turn to food to cope with those things."

"She's been able to overcome that, so I'm very proud of Rachel," he said. "I'm very proud of what she's become. She's the ‘Biggest Loser’ winner, and that's all I know."

Studdard was on the show with Frederickson this season, and they shared the same trainer, Dolvett Quince, but the singing star was eliminated in week 8.

Frederickson, 24, stands at 5'4" and her new weight of 105 pounds is too svelte, according to the Body Mass Index. While the former "American Idol" contestant isn’t shy about giving his teammate props, celebrity trainers Jillian Michaels and Bob Harper said they “weren’t comfortable” commenting on Frederickson’s new figure.

“Bob and I want to take a moment to congratulate all the BL contestants on their hard work,” Michaels wrote on Twitter Wednesday night. “We’re not comfortable commenting on Rachel’s journey because [we] weren’t her trainers and weren’t given any opportunity to work with her at any point.” She added: “Any questions about the contestants on the Biggest Loser should be directed to the show’s producers.”

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