Between the beginning of the film, What's eating Gilbert Grape, and the end Gilbert changes in more then one way. He starts to see things differently and think about things that he never would have thought about previously. The reasons why he is so changed by the end of the film, where he joins up with Becky and her Grandmother to travel around, are because of events such as his Momma dying.
In the Grape family it is quite obvious that the eldest male must assume a leading role that can be very stressful and time consuming. Gilberts father could not handle the pressures and decided to end his life, leaving the leading role to Gilberts elder brother. He also did not want to live with these stress's and left his family and the town of Endora. Gilbert proves to be stronger then that of his brother and father and stays, bearing the responsibility of looking after Arnie, a 17 year old who has autism, his Mum, an extremely obese person who rarely even gets out of the chair, Mrs. Carver, A middle aged woman who is bored with her husband, and generally keeping other people happy. All of these things could be said to "trap" Gilbert, meaning that he cannot do or want things for himself.
Possibly one of the best things that happened to Gilbert was when Becky came into his life. After her Grandmothers car broke down they were forced to stay in Endora until they could get it fixed. It did not take long before Gilbert started talking to her. Gilbert and Becky had many deep and meaningful conversations, but most of those conversations were Becky trying to get Gilbert to understand that he can want things for himself.