Myth: During an 8hr fast, the body cannibalizes muscle tissue for energy and metabolism goes down.
Fact: Bull!#^%. Metabolism actually goes up and you become more alert. In fact, this response goes on for up to 48 hrs and the body does not breakdown muscle during this period. From an evolutionary standpoint this makes sense. If you’re starving, you need to be alert and strong to hunt for the next meal. After the 48 hr period, since there is no food forthcoming, the body goes into self-preservation mode and metabolism slows down and muscle begins to be broken down.