Life of Pi begins with an author's note from Martel that reads "This book was born when I was hungry." Indeed, hunger is a theme that motivates almost every aspect of the plot of the book. Even before his shipwreck, Pi is hungry for knowledge about the world and seeks out men he considers to be wise to learn as much as he can from them.

After his shipwreck, Pi's mind is constantly fixated on obtaining food and water. His mind observes cruel ironies in his new frame of thinking, such as the fact that he is surrounded by water that he cannot drink, or the fact that he was a vegetarian before his ordeal. He begins to reflect on what hunger can do to the psyche of a person and the desperate measures it leads him to, such as his attempt to eat Richard Parker's leavings.

In Part II, it is hunger that brings Pi out of his hoplessness.  He is physically driven to find food and water, and the movement brings him around spiritiually and emotionally as well.  He is finally able to realistically assess his situation on the raft and begin to deal with his bizarre situation.