I don't think anything is ever just one or the other. I would make sure I'm eating slowly and not eating too "long" (it takes 20 minutes for the stomach to register what it has eaten so if you are getting "full" or feeling like vomiting before that, I'd "blame" it on the mental aspect) and would eat the healthiest things I most enjoy for awhile, that make me feel the least sick (i.e., everyone feels sick when they eat too much sugar/candy).