In one scenario, Patchouli comments about a spell that can steal away "unnecessary food" (or thereabouts) from the target. Although the context doesn't make clear whether that means flesh or ki (I'm thinking of the old medieval European claims that witches could inflict impotence, and Taoist thought that if a man...ejects...too much, he'll shorten his life; maybe impotence was caused by a witch draining a bit too much of a man's vital force from afar?).
I thought the food thing was either an assessment based on Remilia's standards or a really surreal misconception caused by Patchouli's extremely bad eyesight...