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AFTER: Rachel Frederickson Fans were shocked when Rachel revealed at the finale that she was just 105 pounds. She had lost 60 percent of her body weight, and people were concerned it was too much. Rachel later said she lost the weight by eating 1,600 calories a day and working out. "I'm extremely proud of the way I lost the weight," she said during a media conference call, per the Los Angeles Times . NBC NewsWire - Getty Images
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BEFORE: Allen Smith Allen, who started at 325 pounds, went on the show because his weight was impacting his career as a firefighter. He also said he was worried that he wouldn't pass his next physical at work. NBC - Getty Images
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AFTER: Allen Smith Allen didn't win season 8, but he definitely accomplished what he set out to do. He lost 116 pounds, or 35 percent of his body weight, on the show. NBC - Getty Images
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BEFORE: Rebecca Meyer Rebecca was 279 pounds when she started the show. She made it to the makeover portion of the show, but unfortunately didn't win the overall title. NBC - Getty Images
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AFTER: Rebecca Meyer By the end, Rebecca lost 139 pounds and nearly 50 percent of her starting body weight, which earned her the $100,000 prize for most weight lost by an eliminated player. NBC - Getty Images
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BEFORE: Bill Germanakos Bill started the show at 334 pounds and competed alongside his twin brother, Jim. At the start, he admitted that he had a "body built by baklava." Steady weight loss, combined with a serious dose of grit, eventually helped him win season four. NBC - Getty Images
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AFTER: Bill Germanakos Bill didn't mess around: He lost 164 pounds-nearly 50 percent of his body weight. Bill later said that being around his family and kids helped keep him motivated. "The Biggest Loser Campus is a place of hope," he told People . NBC - Getty Images
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BEFORE: Michelle Aguilar Michelle started season 6 at 242 pounds and said that she worried her weight was holding her back in life. Michelle competed in the season alongside her mom, Renee. NBC - Getty Images
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AFTER: Michelle Aguilar Michelle ended up winning the title after losing 110 pounds. She later told Access Hollywood that she spent "hours, upon hours, upon hours" at the gym to lose the weight. NBC - Getty Images
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BEFORE: Olivia Ward Olivia started the show at 261 pounds, and competed alongside her sister Hannah. The opera singer said she joined the show because her weight and polycystic ovary syndrome diagnosis meant she probably wouldn't be able to have children if she didn't lose a significant amount of weight. NBC - Getty Images
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AFTER: Olivia Ward Olivia ended up losing 129 pounds and took the title for the season. She's now a senior instructor at SoulCycle. NBC NewsWire - Getty Images
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BEFORE: Hannah Curlee Olivia's younger sister, Hannah, also competed on the show. Hannah started out at 248 pounds, and made it to the final round. NBC - Getty Images
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AFTER: Hannah Curlee Hannah lost 120 pounds, which was 48 percent of her body weight. She didn't win the title, though-she was edged out by her big sister. NBC - Getty Images
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BEFORE: Danny Cahill Danny weighed 430 pounds when he started season 8. He said on the show that he wanted to lose the weight so he could be healthy for his wife and children. NBC - Getty Images
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AFTER: Danny Cahill Danny lost 239 pounds by the end-nearly 56 percent of his body weight-to claim the title. He's kept the weight off and currently runs TheDannyCahill.com , a self-help, motivational company. NBC - Getty Images
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BEFORE: Abby Rike Abby's reason for going on the show was truly heart-breaking: She gained weight after her husband and two children died in a car accident. She weighed in at 247 pounds when she started her journey. NBC - Getty Images
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AFTER: Abby Rike Abby ended up losing 100 pounds, which was 40 percent of her body weight. She's now a motivational speaker. NBC - Getty Images
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BEFORE: Shay Sorrells Shay started season 8 as the biggest contestant the show had ever seen. She was 476 pounds at the initial weigh-in. NBC - Getty Images
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AFTER: Shay Sorrells Shay ended up losing 172 pounds by the show's finale, which was 36 percent of her body weight. She was later challenged to try to lose even more weight by the end of season 9-and she dropped an additional 52 pounds. NBC - Getty Images
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BEFORE: Heba Salama When Heba joined the show, she was 294 pounds. She quickly won fans over with her outspoken nature. NBC - Getty Images
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AFTER: Heba Salama Heba ended up losing a whopping 156 pounds. She didn't win the overall title, but she was named the Biggest Loser of the eliminated contestants and won $100,000. NBC - Getty Images
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BEFORE: Ryan Benson Ryan was one of the original cast members of The Biggest Loser in season 1. He weighed 330 pounds at the beginning of the show. NBC - Getty Images
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AFTER: Ryan Benson Ryan lost 122 pounds-about 37 percent of his body weight-to become the show's first winner ever. Unfortunately, he gained the weight back, but he told Yahoo Health that he's on a new weight loss journey. NBC - Getty Images
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BEFORE: Matt Hoover Matt weighed 339 pounds when he first joined the show. He ended up meeting (and falling in love with) Suzy Preston during filming. NBC - Getty Images
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AFTER: Matt Hoover Matt lost an amazing 157 pounds, which was 46 percent of his body weight, to become the season 2 champ-and he ended up marrying Suzy. They now have two children together. Chris Polk - Getty Images
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BEFORE: Suzy Hoover Speaking of Suzy, she weighed 227 pounds at the start of the show. Like her future husband, she also made it to the finale. NBC - Getty Images
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AFTER: Suzy Hoover Suzy's transformation was jaw-dropping. She lost 95 pounds to end up at 132 pounds by the end of her run on the show. NBC NewsWire - Getty Images
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BEFORE: Erik Chopin The 35-year-old New Yorker was 407 pounds at the start of the show, making him the largest contestant the show had ever seen at that point. Given his size, many people didn't think he could win. NBC - Getty Images
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AFTER: Erik Chopin Erik proved everyone wrong: He lost 214 pounds, which was nearly 53 percent of his body weight. Erik later went on to become a motivational speaker. NBC - Getty Images
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BEFORE: Ali Vincent Ali, who competed alongside her mother in season 5, was 234 pounds at the start of the show. She worked hard and eventually made it to the finale. NBC - Getty Images
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AFTER: Ali Vincent Ali became the first-ever female winner of The Biggest Loser in 2008, losing 112 pounds. She went on to write a book about her experience called Believe It, Be It: How The Biggest Loser Won Me Back My Life . NBC - Getty Images
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BEFORE: Helen Phillips The Michigan native was 48 years old when the competition started. She weighed 258 pounds, with a BMI of 41.5. NBC - Getty Images
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AFTER: Helen Phillips Helen ended up losing 140 pounds, dropping down to 117 pounds at her final weigh-in. She also lost an impressive 54 percent of her body weight. NBC - Getty Images
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BEFORE: Michael Ventrella Michael appeared on season 9 of the show. At the start of the season he weighed 526 pounds, making him the heaviest person to compete on the show at that time. NBC - Getty Images
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AFTER: Michael Ventrella Michael lost an amazing 264 pounds, or half of his body weight. He ended up breaking Danny Cahill's previous record of 239 pounds lost at the finale. NBC - Getty Images
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BEFORE: Jeremy Britt Jeremy was just 22 when he joined the show. He weighed 389 pounds at the start and had a BMI of 59.1. NBC - Getty Images
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AFTER: Jeremy Britt Jeremy became the youngest-ever winner of the show, losing 199 pounds-more than half of his body weight. NBC - Getty Images
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BEFORE: Toma Dobrosavljevic The 36-year-old from Illinois was 336 pounds at the start of season 16. His BMI was 46.9. NBC - Getty Images
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AFTER: Toma Dobrosavljevic Toma lost 171 pounds to become the winner of The Biggest Loser. He beat runner-up Sonya Jones by just one pound, making it the closest percentage between the winner and runner-up in any season. NBC - Getty Images