An ambitious 21-year-old woman who weighs nearly 400 pounds embarks on a one-year challenge in hope of losing weight.

A 23-year-old man tries to fulfill a promise he made to his late mother to lose weight and lead a healthier life.

45-year-old bachelor Dana tries to lose weight and reclaim his life.

Weighing in at 651 pounds, James, a 25-year-old former football player from Fort Worth, Texas, becomes the most obese person trainer and transformation specialist Chris Powell has ever worked with. James must lose 150 pounds to stay on track in the first of his four, three-month phases of weight loss.

A young woman works to lose weight and in the process must face the secret that lead to her becoming obese

Wally, 26, a young father who weighs 490 pounds and whose wife is uncertain if her husband will be around to see their daughter grow up.

Staci, 30, a 456-pound married mom caring for her husband and their two young children, while doing her best to keep a positive outlook.

Krista, 34, a devoted mother whose care for her developmentally-disabled daughter has taken a tremendous toll on her 445-pound body.

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Twins David and Rebecca are split up as they tackle a 90-day weight-loss challenge.

An adopted woman named Meredith tries to reach her goal weight of 155 pounds and gain the confidence to contact her birth mother; Meredith receives a visit from actress Nicole Eggert.

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Chris helps a woman -- who blames her obesity for her daughter's death -- to get healthy.

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Avid basketball fans, twins Robert and Raymond -- who start out at 381 and 378 pounds, respectively -- get the chance to meet players Kobe Bryant, Steve Nash, Byron Scott and James Worthy along their weight loss journey.

A tragic accident inspires a 399-pound firefighter to change his life; a 331-pound former college basketball player wants to overcome her depression and reclaim her life and her health.

Chris and Heidi help a formerly fit couple get back in shape for their wedding day; David Tutera, Rocco DiSpirito and Duff Goldman help the couples plan their big day.