Amy sees a pediatric dietitian and faces some difficult truths about Gage's diet. Dr. Smith makes a house call and confronts Tammy about her partying lifestyle. While on the road with Chris, Tammy's health hits a dangerous low point.

Amy and Michael finally move out of the duplex, while Tammy's partying phase takes a turn for the worse. Amanda tries to get through to her sister before it's too late, and Amy's in for a rude awakening at her annual check up with Dr. Procter.

After a rift on the family vacation, Amy returns home and drops a bomb on Tammy. While Amy focuses on her new life, Tammy makes a decision that takes her even further away from her weight-loss goals.

The family vacation starts off terribly when Tammy refuses to enter the cabin; Chris hopes he's lost enough weight to fulfill a life-long dream.

While Chris makes progress after his surgery, Tammy gets discouraging news; Amy plans a unique bash for Tammy's 35th birthday; the family excitedly plan their first vacation together with all five siblings, but concerns rise about Tammy's mobility.

Chris faces a weigh-in to get approved for bariatric surgery; with Tammy's weight at a standstill, Amy and Michael make a life-altering decision; the family's fears about Tammy's choice in partners are realized.

Tammy must see a new therapist, but things don't go the way she'd hoped. Amy wants to lose her excess skin, but she gets bad news at the plastic surgeon's office. Chris faces the scale. If he's below 400 pounds, his surgery is on.

After Tammy's bad doctor's appointment, Chris comes down on Amy for enabling her sister. The family worries Tammy's new boyfriend is leading her down the wrong path. Amy's idea of having a meet and greet to help Tammy has its own set of problems.

When Amy tries to get her house in order, she must confront some demons from her past. Tammy admits to a few cheat days just before her first doctor's appointment since rehab. Chris steps on the scale that could change his life.

Amy is upset that Tammy's new nurse isn't pushing her enough. Tammy has started slacking, and the family worries about what could be the cause. Chris and Tammy clash when he confronts her about the new man in her life.

Tammy is back from rehab, and Amy comes to a drastic decision regarding her sister. With his bariatric surgery on the line, Chris tries to shed weight.

Tammy makes a life-altering decision. Amy finally gets a taste of the life she's always wanted, and an emergency surgery has repercussions for Chris.