The three core endings:
1) Reach final weight without enlisting help of Donna. The hint on how to get her on board appears in the Quick Start Guide. This ending is the most brutal and unsatisfying, and lacks some back story elements.
2) Get Donna’s help, but say “no” during the “Guinness Records” event. Still very bitter-sweet.
3) As above, but answer “yes” during the same event. The closest you get to a happy ending. ^_^;