READ PART 1 HERE
Won't I be be incredibly hungry when I don't eat for such a long time?
Your body's hormones are trainable. If you eat several small meals a day, your body is literally going to expect you to feed it all the time. If you only eat a few large meals a day, your body's ghrelin (hunger hormone) will be much less likely to turn on you. Personally, I was only more than marginally hungry for the first few days while changing my eating habits around. The body is extremely adaptable to change, and changing your meal frequency on it isn't going to make much of a difference.
Also, and I'm sure many of you have heard the term, but your body won't go into starvation mode by not eating for 16+ hours. You can go into a form of starvation mode due to metabolic damage from constant lack of calories due some stupid fad diet, yes, but not from simple fasting. It's going to take you somewhere around 60 hours of fasting to significantly lower your metabolic rate.
Won't not eating for such a long time cause me to lose muscle mass?
This is a basic rundown of how your body would waste muscle. As many people know, the body, and more specifically your brain really loves to run on glucose aka blood sugar. The most obvious way to keep a stream of glucose in your system is to eat carbohydrates regularly. This will pretty much ensure round the clock streams of the stuff running through your system.
But what happens when you don't eat for 16+ hours? Your last meal of carbs is long digested, and now your brain is hungry for some glucose! Your liver is the body's backup mechanism for glucose, as it stores glycogen which can quickly be converted into glucose for fuel purposes. An average 150 pound man can hold up to 120 grams of it, which roughly equates out to around 500 calories worth of energy. However, especially if you are keeping carbs low or in my case hardly having any at all, your liver will run out of glycogen.
After this happens, the body looks to start using free amino acids in the blood to convert to glucose. Luckily, your body fat is capable of breaking down into free fatty acids which can be used for fuel, as as well as glycerol, which can be turned into glucose. This can be responsible for a large portion of glucose management in your body, and yet another reason why fasting is so great for body fat loss.
Body fat isn't responsible for 100% of the glucose management, though, which leaves only one other issue. That is the amount of free amino acids in the blood stream from protein you've eaten. If you don't have any of those available to use, then and only then will your body start using up muscle for fuel purposes. Your muscle is largely made up of protein, which in turn is largely made up of amino acids, which is why it will be the next target for glucose making purposes.
However, there is a near 100% guaranteed way to make sure it never gets to this. If you're eating protein rich meals, especially slow burning proteins such as eggs, beef, and casein protein powder, you body will be supplied with a steady stream of amino acids up to and long after the 16+ hour mark. This is a huge reason why fitness professionals encourage most clients to eat at least 1 gram of protein for every pound of lean body mass (muscle) every day.
Bottom line. If you have body fat and eat protein rich meals as suggested, IF isn't going to cause any muscle loss. Period!