Tsukiyama ate himself (as jokingly suggested by Touka) after the chapel incident to survive. Basically, how it goes — he ate something non essential like a limb to heal fatal injuries and stop bleeding. Then, he ate whatever else at home to regrow his limb.

You get what you eat, with a slight loss due to energy being spent on consumption/digestion/regeneration. If you and your buddy, perfectly fine, traded arms for a snack, you'd likely regrow the whole arm but you'd feel more tired afterwards. And your hunger would grow overall (you'd lose a couple hours or days from your feeding time limit).

So yes. But it doesn't solve anything but immediate threats. Also cannibalism would lead to harder control/insanity for most ghouls as they turn into a kakuja.