From Science News: "the cells of organisms from yeast to humans regularly engage in self-cannibalism. Cells chew on bits of their cytoplasm - the jellylike substance that fills their bellies - and dine on their own internal organs ... It may sound macabre, but gorging on one's own innards, a process called autophagy, is a means of self-preservation, cleansing and stress management. ... A munch here gets rid of garbage that might otherwise clog the system. A nibble there rids cells of malfunctioning parts. One chomp disposes of invading microbes. In lean times, all that stands between a cell and starvation may be the ability to bite off and recycle bits of itself. And in the last decade or so it has become clear that self-eating can also make the difference between health and disease. ... Starvation inhibits an important biological signaling system, known as the mTOR pathway - named for a key protein involved in regulating cell growth and survival, cell movement and protein production. The inhibition of mTOR sets off a cascade of reactions inside the cell that end in autophagy and may be crucial to prolonging cell life and ultimately fending off cancer. A drug that inhibits mTOR, called rapamycin, has been shown to extend life span in mice. It and calorie restriction are [amongst a handful of] methods proven to prolong longevity, suggesting both may work through autophagy to make cells live longer."