Food. It was always about food. It was a tool of control used by the Germans to dehumanize these prisoners. How many times do we see Elie and others fight and claw and even kill for bread. It turns sons against fathers and fellow man against fellow man. The value of the bread is greater than the value of a soul.
I think you can relate Maslow's "Heirarchy of needs" to this novel. You can google it to find out more about it, but centrally what we see in this novel is life stripped of all hopes and aspirations and reduced to mere animal instincts for food, shelter and safety. We see the author going through this process himself as he is forced to focus on only the bare necessities to ensure his survival. In the face of this tremendous battle, all other concerns such as love, relations and friendship are lost as each Jew seeks to survive.
Survival. It as this point in the work where we begin to see the life aspect to Eliezer take on the meaning of survival. One critical element of this chapter and those that follow display the reality that the Nazi treatment of so many robbed them of "living" life through dehumanization. In the process, many might have been living, but they had stopped living a life worth living when captured by the Nazis. This chapter in the book marks the point where life became about survival, losing any element of being "human in the process.
The only things that Elie took interest in were his bread and soup. This is stated in the book at the very end of the section where Elie describes his encounter with the camp dentist and explains how he managed to keep from having his gold crown extracted. He writes, "Bread, soup--these were my whole life. I was a body. Perhaps less than that even: a starved stomach. The stomach alone was aware of the passage of time" (Wiesel 50). He is trying to explain why he could not feel remorse or sorrow for the fact that the dentist was sent to prison to be hanged, why he actually felt pleased with the turn of events. It is another way to show the loss of humanity and faith he reached while in the hands of the Nazis.