Some fans of NBC's weight loss reality show "The Biggest Loser" are expressing outrage over the show's latest champion: 24-year-old Rachel Frederickson, who lost 60 percent of her original body weight to win the $250,000 grand prize.
Frederickson, a former competitive swimmer and current voice-over artist from Los Angeles, started the season at 260 pounds and weighed in at 105 pounds by Tuesday's finale. When she emerged on the stage for the last show, cameras panned to shocked "Biggest Loser" trainers Bob Harper and Jillian Michaels, who clapped slowly but seemed to mouth, "Oh my God."
Frederickson, whose height has been reported as 5'4" or 5'5", is now underweight for her frame, according to the body mass index chart. The 155-pound loss over approximately five months (the filming schedule as listed by the show) means that she lost an average of about one pound per day.
That's a far cry from two pounds per week, which is the upper limit of what most doctors and dietitians recommend for their weight loss patients. But a 2013 meta-analysis of myths around weight loss and obesity research, published in the New England Journal of Medicine, found no scientific evidence that supports slow and steady weight loss over rapid weight loss. In fact, there's not even a good threshold for defining what "rapid" weight loss is, said assistant professor Krista Casazza, Ph.D., R.D., the lead author of the analysis.
Losing one pound a day, Casazza told The Huffington Post, isn't healthy for the average person. But Frederickson wasn't the average person.
"Rachel is young and a former athlete, and she likely had more lean mass than others in her position," Casazza said. "She was metabolically programmed differently than an ordinary person, and you have to take all of that in context when you talk about healthy pace of weight loss."
Casazza, who has not personally evaluated Frederickson and is not affiliated with the reality show, is an expert on body tissue partitioning (the interplay between fat, bone and muscle) at the University of Alabama at Birmingham -- and also happens to be a fan of "The Biggest Loser." Based on her research, Casazza had also predicted that Frederickson would win this year's competition. But she's still disturbed by the end result.
"Up until the final episode when she was losing weight with the trainers, not at home, she looked a lot healthier and looked like she was preserving the bone and lean mass," said Casazza. "In the final episode, she looks emaciated."
A screenshot from the "Biggest Loser" finale, which compared Frederickson on the right to a hologram of how she looked at the beginning of the show.
Weight loss as rapid as Frederickson's could result in a loss of bone mass and an increase in bone marrow fat, explained Casazza, which might set a person up for cardiovascular problems like heart attacks and high blood pressure, as well as increased risk of fractures. To prevent this, Casazza recommended that Frederickson work her way back up to 120 lbs. -- even 130 lbs., considering how muscular she is.
"When you start losing bone and muscle mass, you have all kinds of problems that can manifest," Casazza said. "Even a specific amount of fat is required for physiologic function."
Like Casazza, Susan Bowerman, M.S., R.D., assistant director of the UCLA Center for Human Nutrition, emphasized body composition as the true marker for determining a healthy weight.
"It's not just a question about BMI," said Bowerman, who also hasn't medically evaluated the contestant and isn't affiliated with the show. "It's about what that weight is composed of."
Bowerman declined to speculate about Frederickson's health because "The Biggest Loser" doesn't make public statistics about its contestants' body fat percentage or lean mass percentage.
She also said it was understandable that a weight loss program that is supervised and supported with many interventions, like that of "The Biggest Loser," results in faster loss than the efforts of the average person attempting to drop pounds without a doctor's help. But Bowerman did warn that drastic weight loss, which strips away lean mass in addition to fat, is harmful over the long haul.
"Over a long period of time, [drastic weight loss] is somewhat like when people are starving," she said. "You could break down muscle tissue and other organ tissue."
In some cases, a person could even end up with more body fat. For instance, a repeated cycle of loss and gain might leave someone with a higher body fat percentage but less muscle to help regulate weight.
"Maintenance for most people is a lot harder than losing," Bowerman said. "If someone gains a lot of the weight back, it suggests the changes were too drastic."
"The Biggest Loser" has come under fire in the past for its weight loss methods, which have included pushing contestants to compete to the point of hospitalization and to take caffeine supplements.
The most damning critiques come from some of the contestants who defied their strict nondisclosure agreements to shed light on the weight loss methods that they say the show encouraged. Ryan C. Benson, the very first winner, told The New York Times in 2009 that he urinated blood because of the extreme dehydration tactics he used to drop 122 pounds for the finale.
In 2010, season three finalist Kai Hibbard told told body image coach and writer Golda Poretsky that trying to lose weight for the finale left her so weak and defeated that her family staged an intervention to deal with the new eating disorder she said she had developed.
NBC did not respond to HuffPost's request for comment. Watch this season's finale reveal in the video below: