There was a Stephen King story about a doctor who was shipwrecked and stranded with no food. It got so bad that the only way he could survive was to amputate his legs, surgically repair himself, then cook and eat his own flesh. Eventually got rescued.
Sounds rather dumb. The body naturally consumes fat and muscle tissue when starving. Probably far more efficiently than eating your own meat. Having a serious wound like an amputated leg also wastes energy.