Summary: With her weight spiraling, Tammy makes a life-altering decision.

Summary: Tammy is back from rehab, and Amy makes a decision regarding her sister.

Summary: 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.

Summary: Amy must confront demons from her past, and Tammy admits to cheat days.

Summary: Chris comes down on Amy for enabling Tammy.

Summary: 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.

Summary: Chris faces the ultimate 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.

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

Summary: 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. A last attempt to save the vacation ends in another confrontation. The siblings discover Tammy's secret.

Summary: 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.

Summary: 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.

Summary: Amy sees a paediatric 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.