Twins David & Rebecca didn't think that much about their weight as they were growing up in North Prairie, WI. David, who weighs in at 470 pounds, and Rebecca, who weighs 398 pounds, spent their childhood making people laugh. Behind the smiles there were tears of pain from a difficult upbringing that led them to use food as an outlet. After Chris Powell decides to help the twins on their 23rd birthday, he realizes they're extremely co-dependent and enable each other's poor decisions, especially when it comes to their weight. After a tearful goodbye, the twins are split up for a 90-day challenge, with Rebecca going to Arizona to work alongside Chris's wife, Heidi. At the beginning of his weight loss journey, David said he'd always wanted to go through Navy SEAL training to show his dad that "he was a man." Chris takes the twins on his toughest milestone challenge to a rigorous "Kokoro" training camp designed to forge mental toughness and modeled on Navy SEAL Hell Week. But when the twins' old habits begin to reemerge, Chris becomes concerned they may not be able to meet their weight loss goals.