The film 'What's Eating Gilbert Grape' encompasses many issues that answer that question. There are countless issues that bother Gilbert in the film which are hassling him and are hindering him from living a 'normal' life. Issues such as the amount of responsibility he has, the fact that he can't leave Endora, his relationships with Becky and his affair with Mrs Carver are all frustrating and obstructing him from moving on. Gilbert has the responsibility of looking after Arnie, as he is mentally handicapped. He looks after Arnie because he is his brother ad also he feels that he is responsible for what happens to his family members. Arnie dependence on Gilbert and his frustrating behaviour really gets to Gilbert at times and Gilbert is forced to care for him as his mother is unfit for parenting.
This is also another issue for Gilbert. He is embarrassed by his mother, Bonnie, because of her size. This is evident throughout the film. Because of her obesity she is house bound and Gilbert is forced to act the father figure, which adds to his responsibility. He is the only one who has a job and has to provide an income to support his whole family, which doesn't leave much for him. He is seen throughout the film as the parental figure where all of the family members depend on him and he also has to act as the man of the house by organising the repair of the house and things like that.
Gilbert can't leave Endora because he has too much to look after, like his family and his house. He is not stopped physically from leaving Endora but he feels he has too much responsibility and just can't leave it all behind. This leads me to Becky. Throughout the film her character tries to beckon him beyond of Endora and he falls in love with her, which in the end helps him to move on. He feels like he doesn't want to get her involved with his family because he is embarrassed of them and he doesn't want her to think that he is a freak. All these issues are tied back to the title of the film in the sense that all these obstacles that he has to face are eating him inside and he feels that he needs to break free from all of his responsibilities and live a normal life.
All these issues answer the title of the film.