Before taking any psychedelic, I try to avoid eating for at least a couple hours. My normal scheduling is something along the lines of: moderate meal a couple hours before bed the night before, wake up and have a drink or two and maybe a handful of peanuts or something to get my metabolism going, shower and finish waking up, then dose around an hour or two after first waking up. Even when I haven't eaten in ages I find it hard to muster an appetite upon first waking, so I find this schedule makes it easy not to be hungry until hours later when I can eat on just about any psych.
How soon I'm willing to eat and what I think I can stomach varies from trip to trip and substance to substance. LSD comes to mind as having little to no body load; I can eat pretty normally once I've waited a couple hours to avoid slowing the onset.
The more of a body load a substance produces for me, the less inclined I am to eat. Any drug known for causing nausea is one I avoid combining with food. When I used to shroom semi-regularly I would pretty much never eat until well into the come down. On 2C-I, I usually subsist on smoothies and other drinks until the come down as well. While I don't get nauseous on 2C-I and the body 'load' generally combines with the euphoria into a pleasant sensation, I still get the distinct feeling that eating anything too substantial would not feel as good as leaving my stomach empty.
All that said... When I'm hungry and tripping, spend a while worrying about whether eating is a good idea and then finally do eat and don't experience any nausea or increase in negative body load, it's a truly rapturous event.
