x1 (partially) eats itself/performs autophagy.
This word is broad: It encompasses the actual act of biting into one's own body, removing a segment therefrom, and swallowing it; but it can also include usage of fat stores, dystrophy of muscles, etc. due to starvation, even if no biting occurs. Thus, it is technically happening (at least according to wide definition) much of the time, even if unnoticeably so. It is always a form of mityjutcti.