if youre wondering what heathfield is talking about, i believe your body begins to break down its not so vital organs in order to keep the vital organs alive for longer.
if you was to cut your arm off in anticipation of starvation, then i would assume that the nutrients that are currently being pumped around your body would ommit feeding the muscles in the missing arm, thus allowing the nutrients to feed other parts of the body for longer. eating said arm would provide extra nutrients which in turn would feed the rest of you.
so yes. if you cut off your arm and ate it, without bleeding, or at least drinking the blood, then you would live longer. the less vital organs your body is feeding the longer the vital organs can be sustained. so in times of starvation you should eat both arms, both legs, your bum cheeks etc