different story, the controversy over t"the biggest loser," stunning weight loss for Rachel Frederickson has many wondering if she's putting herself in danger by losing so much weight so quickly. Now... See More
different story, the controversy over t"the biggest loser," stunning weight loss for Rachel Frederickson has many wondering if she's putting herself in danger by losing so much weight so quickly. Now she's answering critics. ABC's linsey Davis has the story. Lost 155 pounds. Reporter: From the moment the most recent winner of NBC's "The biggest loser" stepped on the scale revealing her 105-pound, critics have been weighing in calling her anorexic and frightening emaciated but now Frederickson is defending her weight to "People" magazine explaining how she lost 60% of her original body weight, the most in the show's history. The 24-year-old says in the four months after the show she lost an additional 45 pounds before the finale by eating 1600 calories a day via five small meals and maybe three, four classes a day including Zumba and spin. In an interview set to air on "The Rachael ray show." Bob Harper says what people don't understand is when the contestants leave to go home they're in charge of themselves so when she walked out I was just kind of like, whoa. Susan Rappaport who lost nearly 120 pounds herself and now runs a fitness studio in New York says she's concerned about Frederickson's well-being. She's going to have to modify her diet in order to maintain where she is now. That's where extreme eating disorders are born. Reporter: According to the "Ladies' home journal" the idea weight for a a'5" small frame woman is 114 to 123 pouchdzs. Based on that recommendation Frederickson is nearly ten pounds underweight. Obesity and anorexia are on the same spectrum just at opposite ends. It's not uncommon for one eating disorder to basically transition into another eating disorder. Reporter: Even the fashion industries in certain countries ban models with less than 18 1/2 body mass index from walking the catwalks. Frederickson's bmi is now 18. When asked if she reached a healthy and sustainable weight, Frederick's response, "Absolutely." For ABC news, linsey Davis. Deading herself.
This transcript has been automatically generated and may not be 100% accurate.