The easiest way to make the worst possible meal is to make kibble out of human meat. This way whoever eats it gets the -15 human meat mood debuff and the -15 ate kibble debuff. If you can be arsed to do a not worthwhile amount of micromanaging, you can make human meat + insect meat kibble to make it even worse.
I guess if you really wanted the min/max the meal debuffs, you could make separate stacks of kibble, one for each "bad" food ingredient. Set up a kibble buffet and lock the victim in a room until they've sampled one of everything from the poop kibble buffet. I've had at least a combined -75 mood from stacking bad food mood debuffs before.
Do you have your colonists restricted off the survival meals? That's usually what happens to me when I forget to update them to the caravan meal restriction before I send them.
Edit: Nvm, just saw your edit. Caravanning is just dumb
I've been getting this message a lot in 1.5 - it may be bug. I've yet to have people actually get hungry on a caravan, but my trips are also 3-4 days max. (I cut my time in half by far-skipping back.)