Chris turns Dave and Becca over to the SEAL team trainers. The twins are challenged to a rigorous "Kokoro" training camp designed to forge mental toughness and modeled on Navy SEAL Hell Week. Becca struggles mightily during the beach run. She’s terrified when she’s told to link arms with the others while lying in the ocean. Her coach pushes her to run back to the gym. Becca collapses before they get there. She works through a panic attack to get back up. Dave is happy to have her back. Becca takes charge of the rest of the grueling workout. This inspires her brother to continue.
Dave and Becca must lose a combined 76 pounds for Phase 3. Trouble arises. Dave doesn’t want to always exercise and Becca takes cues from him to possibly binge. The two of them argue about this issue. Becca feels like she’s being sabotaged by her brother. At the 9-month weigh-in, Chris notices the confidence in his clients. He also learns that they are struggling with their relationship with each other.
At the weigh-in, Dave is shown to have lost only 28 pounds. As for Becca, she’s dropped 20 pounds. They didn’t meet the goal, but they have chopped a significant chunk of their body fat. Dave is a good candidate for the skin removal surgery, but his sister is not. This has him feeling guilty about how he treated Becca over the past three months. For the final phase, the twins are separated once more. Dave begins his journey by telling his dad about his suicide attempt by drugs. He says that a phone call from his father where he said that he loved him was all he needed to turn things around. His dad saved his life.
The time comes for the final weigh-in. Dave steps out to the cheers of an amazed crowd. He gives his dad a hug before taking the stage. Dave hasn’t seen his sister in three months. He’s blown away by how great she looks when she joins him on the stage. Tears flow. Dave steps onto the scale to see his new weight of 258 pounds! He lost a total of 212 pounds over the course of a year. Becca is up next. She weighs in at 192 pounds. She lost 206 pounds! She’s now a candidate for the skin removal surgery. Combined, Dave and Becca lost a total of 418 pounds! They are a new generation wonder twins!