In his introductory note, Yann Martel says, “this book was born as i was hungry”, what sort of emotional nourishment might “Life of Pi” have given to its author?
We should note that the author's introduction to "Life of Pi" is probably fictional. It is merely a story-within-a-story that is meant to lend some depth and legitimacy to the narrative. This method of introduction has been more or less common throughout the history of literature, although if you look at the Romantic/Gothic period there is an abundance of "found" stories, such as those where a diary or a message in a bottle leads the narrator to the rest of the tale, putting the reader in the place of being just as skeptical as the narrator.
The statement that the author was hungry is not literal, but metaphorical. The author has failed to gain notice for their writing and is seeking inspiration and, ultimately, a successful book from the perspective of sales and reviews. The author craves legitimacy and inspiration. We might also interpret this to mean that the author was literally hungry, or nearing hunger, due to not having an income from their writing, but I think this is disqualified by the fact that they had enough money to travel to India.
I think the "emotional nourishment" was found in the story being unique, meaningful and just fantastic enough to feel both believable and fantastic; it was exactly the sort of story that the author wanted to write. We might go further and analyze the actual content of the story and hypothesize its effects on the author, but I don't think this is relevant to the author's initial position. For example, the story is said to "make you believe in God" but this concept is introduced long after the author makes this initial statement, so I don't think it can be construed that the author is hungry for spiritual belief.