I don't know, maybe body load is a term I am using incorrectly. Things were much simpler before the internet, we did not have all this knowledge to encumber us ;-).
Maybe someone can correct me if I am using the term wrong, or if it is a catch all phrase.
It seems some people are describing things like "nausea" whereas other people are describing heaviness which I agree is part of doing shrooms but not even close to the level of ingesting a lot of marijuana. I see those as usually two different things, although both to me can in fact be very unpleasant.
To me body load is something like 2C-E where I have this sense of uncomfortable heaviness and physical unease that seems less a part of the effect and more a part of the side effect.
On mushrooms I may experience a brief sense of physical nausea, but it is from the ingestion act, and passes quickly, and is not part of the actual "drug experience"
After mushrooms kick in I feel this intense sense of "intoxication", and also moments of "heaviness" but it is not something I would describe as "body load" but rather a part and parcel of the total experience.
On LSD I could have moments of uncontrollable hilarity and be inclined to also need to move around. On mushrooms I could have moments of uncontrollable hilarity where I am compelled to lie on the floor in a fungal stupor. Alcohol I could have moments of uncontrollable bad judgment where I am compelled to lie with an ugly woman I just met in a drunken stupor.
All have their own "body" effects, and especially alcohol where not only do you wake up hungover as shit, you also may have to gnaw your arm off when you look at the coyote woman next to you. But that is not really how I would define "body load". "Body load" to me is say the 2C-E feeling where I have to go lay on the bathroom floor, not because of a sense of stupor, but because it is comfortingly cool and reassuringly near the toilet.
Does that make any sense?