The Four Nutriments: what do the metaphors in SN 12.63 mean?
The Four Nutriments ('ahara') of physical food, sense contact, intention &amp; consciousness are true for the worldlings who have craving (tanha) and greed (lobha) or aversion / revulsion (dosa), caused by ignorance (moha).  Tanha, lobha, dosa, moha provides nourishment for the continuation of life from existence to existence. 

The worldlings have  five aggregates of clinging (Panca Upadana Khandas).  In the case of Arahants – the awakened ones - there is no craving. They have rooted out the “I concept”.  They have fully realized five groups of existence and the five grasping groups of existence (Panncakkhandha and panca upadanakkhandha) .  Arahants have only the five aggregates in detachment  (Anupadana).  Upadana means ‘grasping’ and Anupadana means ‘non-grasping’ or letting go.While Upadana leads to Samsara, Anupadana leads to Nibbana.

To put it in another way, (for better understanding), after the elimination of all defilements an arahant lives in society without Upadana or Attachment to any thing in the world. He does not have the five grasping groups (pancaupadanakkhandha) but only five groups,aggregates (Pancakkhandha), namely, rupa (body), vedana (feeling), sanna (perception), sankhara (volitional formation), and vinnana (consciousness).  His consciousness is ‘translucent’ (for wont of a better word) as no food is provided. In this he is immeasurable - is like the Buddha. All measurement is from a here to a there, with in-betweens. In the Buddha, there is neither a here nor a there nor any in-between. He is thus immeasurable. See Bahiya Sutta: About Bahiya - Ud 1.10


  “Then, Bahiya, you should train yourself thus: In reference to the seen, there will be only the seen. In reference to the heard, only the heard. In reference to the sensed, only the sensed. In reference to the cognized, only the cognized. That is how you should train yourself. When for you there will be only the seen in reference to the seen, only the heard in reference to the heard, only the sensed in reference to the sensed, only the cognized in reference to the cognized, then, Bahiya, there’s no you in that. When there’s no you in that, there’s no you there. When there’s no you there, you are neither here nor yonder nor between the two. This, just this, is the end of stress.” (Ud I.l0)...


An arahant is sustained by ONLY the physical food that does not create upadana. He does not have the other three ‘mental’ foods as he has rooted out the “I concept”.  He is free from attavada upadana by seeing it as a deceit (the true nature). So if there is no nutriment  consciousness, an Arahants  consciousness is mere presence.  Since there cannot be presence without something being present, it is what distinguishes living from non-living, such as tables and chairs. The Buddha has stated that consciousness is dependently arisen, since without a condition there is no origination of consciousness. In an Arahant, Paticcasamuppada (dependent arising) ceases.  Which means Vinnana paccaya (conditioned by consciousness) too ceases.