While published reports have said Gosling left Peter Jackson's production because of creative differences, a source told Us magazine the 26-year-old actor "was fired" because "(Gosling) just gained too much weight."
"He ate grilled cheese every day," said a second insider, adding: "He drove the hair and wardrobe crew crazy."
Gosling, who told reporters last month that "The Lovely Bones" "is a totally unique story," said of his departure from the production, "The film is much better off with Mark Wahlberg in that role."
The book is about a 14-year-old girl who is raped and murdered, then watches her family and killer from heaven.
Wahlberg, 36, takes over the role of the girl's grieving father.