The theme of starvation is something that is present throughout the text because of the way in which Lazarillo is shown to live in such want and desperate circumstances, even when there is plenty of food about him. For example, when he is serving his master the priest, he is only allowed an onion every four days, and depends upon funereal feasts in order to avoid starvation. Eventually he is forced to steal the bread that the priest keeps under lock and key but do so in a way that makes it seem as if mice are eating the bread. Want is something that characterises Lazarillo's life and his lowly status in society.
However, we need to remember the kind of literary genre of this book and how starvation fits into this genre. As a picaresque novel, the story focuses on the experiences of a rogue who is also the novel's first person narrator and protagonist. A picaro is normally thought to mean a poor wandering rogue who is forced to survive by his wits alone as he operates on the edges of a society where social status is everything. Survival is only possible for the picaro by sacrificing personal ethics and values, or concepts of right and wrong, to the brute necessities of making it through each day.
As the picaro serves a number of masters, the picaresque novel allows the author to satirise a large cross-section of society and to expose the various ills and foibles of society in the face of poverty. The starvation theme in this text therefore helps to establish Lazarillo as a picaro, and to identify his want and dire situation in the face of the luxury in which so many of his masters and other characters seem to live.