It's not like your body is going to eat its own muscle! It's not that stupid. The muscle loss is due to the normal wear and tear of daily activities. If you train hard during a prolonged fast, it's likely going to lead to more muscle breakdown. And autophagy is not that either. Also, it kicks in much sooner than 5 days.
As for fat reserves, even fairly lean individuals can probably go a week or two without food without breaking down much muscle. 14 days at 2500 calories is merely 10 pounds of fat. Unless you are morbidly skinny, you should have 10-15 pounds of fat ready.
As for fat reserves, even fairly lean individuals can probably go a week or two without food without breaking down much muscle. 14 days at 2500 calories is merely 10 pounds of fat. Unless you are morbidly skinny, you should have 10-15 pounds of fat ready.