ive ripped a couple of posts from a body building thread that everyone might find interesting
first post:
Hunger doesn't mean muscle loss. In fact, most of the time it doesn't even mean you actually need to eat. Limbic Hunger is mental, and it causes you to be hungry around the times you normally eat due to the release of grehlin, which increases hunger and rises when you're in anticipation of a meal. Somatic Hunger is actual physical hunger that occurs when your stomach has been empty for a while. Grehlin can be released then as well.
Leptin increases hunger when body fat decreases, but it doesn't just increase when you 'don't cheat', and a cheat won't 'reset' leptin levels.
A lot of things cause hunger, so keep that in mind. Morbidly obese people don't stop getting hungry, despite the fact that they have plenty of body fat to use for energy.
Therefore, you can be hungry for many hours before actually losing any muscle. Fast for over a day, and then you might lose some muscle.
second post
Here's the thing- you pretty much ARE always undergoing catabolism. But guess what? You're also performing anabolism all the time too! Catabolism = breaking down. Anabolism = building up. These words aren't just associated with muscle (except on bb.com). Your body is constantly breaking down dietary nutrients and synthesizing protein, glucose, and triglycerides your body can actually use. You're also constantly tearing down and repairing muscle tissues. Your bodily functions never stop, and catabolism and anabolism follow a natural cycle for repair and growth. You catabolize fat for energy LONG before you catabolize muscle. Think in terms of days, not hours.