Sara G. gets a hungry no-prize for bringing us this discussion of what happens when the "dietary dingus" is removed from a fly, causing it to never feel full:
Such a fly began to eat in the normal fashion, but did it stop? Never. It ate and ate and ate. It grew larger and larger. Its abdomen became so stretched that all the organs were flattened against the sides. It became so big and round and transparent that it could almost be used as a miniature hand lens.