I often talk about how many items you can find in the supermarket are ‘Not Food‘.
The other day I took a stab at defining what food is to me:
For me, food should be mostly: satisfying, have no ingredient label (or, as few ingredients on the label as possible), agree with my body (specifically, not disrupt my bowel movements or make me feel bloated), high quality (organic, grass-fed, pasture-raised, biodynamic, or similar), and fresh (meaning, probably not last indefinitely on the shelf).
Matt Fried 