My siblings and I, through rigorous hypothesizing, game theorizing, and quantitative and qualitative testing, have come up with the four major motivations for eating. They are: (1) hunger, (2) boredom, (3) principle*, and (4) spite. As an example of the last, I present the following:
MP: omg are you home?? i'm totally making you take me to the airport. i'll take you to chipotle!!
mikaydee: haha, no. i'm at work!
mikaydee: [RM] could take you to the airport
MP: fine i don't know how you can pass up an offer like chipotle
mikaydee: i'm at work!
mikaydee: and can get chipotle on the way home
mikaydee: which i will now
mikaydee: just to spite you
mikaydee: a spite burrito!
mikaydee: mmmm, the most delicious kind....
*Often accompanied by observations such as "wasting food is a sin," or "there are starving children in [generically poor developing nation]"