With fasting the body chooses a mixture of stored body fat and lean body mass as fuel. Just as the body taps into body fat and breaks it down to use as energy, it can do the same with muscle and organs. When deprived of food the body can easily break down the heart, the liver and other organs to make fuel. The body will also rip apart the muscles to make fuel during a starvation fast.
This can lead to exhaustion and eventually death.
So we can conclude that the fast isn’t the smartest approach to fat loss..
Once people figured out that prolonged fasting worked but the negative was death they began to alter the fasting approach to weight loss and the modified fast was born.
The modified fast involved abstaining from food completely for as long as you could and when you finally broke down, your willpower was crushed and your appetite screaming in high gear you would eat. Some would eat a small amount and drink a ton of water to suppress the appetite. But others would go crazy, break down and eat as if it was their last meal on earth, probably negating any fat loss during the period of fasting