My off the cuff idea is if a human is host to worms then it is feeding a guest.
If worms are feeding on our digested or perhaps to much high fat/portion size ect then the worm is just eating what our body cannot absorb.
Hmm sound like a diet wieght lose program to me.
of course puking them up or pooping them out if they over multiply could be a huge freaky moment.
I had a patient with an eating disorder who ate fleas. She was hoping to get tapeworms from them. Ooooh, the quest to be skinny.
Earlier last century, a French diet pill did indeed contain tapeworm eggs.