I'm confusing about a sentence written by my friend. Which was said "I eat a curry rice at the expense of shitting." It seems that he wants to express "I eat something than I'm stomachache later." But the question is how to use the phrase "at the expense of..." Is it correct that my friend said? Or it should be "I ate a curry rice at the expense of diarrhea." Which is correct, both or neither? Thanks for all your answers and judges.
The phrase "at the expense of" means that you are sacrificing something else:
so as to cause harm to or neglect of.
"the pursuit of profit at the expense of the environment"
synonyms: sacrifice, cost, loss
"the imposition of stringent pollution controls will come at the expense of jobs"
In this case, the examples you have given are correct, since you are showing that eating the curry rice will have a negative effect which you know about: "At the expense of having diarrhea".
"At the expense of" doesn't mean one thing will cause another thing, it means that you do something knowing that it will have a negative effect on something else, but you think it's a necessary sacrifice.