It always amazes me how some people think they can get through a difficult workout without the proper fuel. For example, I once talked to a guy in gym that had gone most of the day without eating so much as snack.
Granted, he ate a pretty good breakfast, but then he went for the rest of the day barely eating anything. It was now pretty late into the evening, and he was about to begin some pretty serious weight training routines. I couldn't believe that someone who was trying to build a significant amount of muscle would try to do so on an empty stomach.
When I protested, he assured me that he wasn't even hungry. That may have been the case, but it doesn't mean that it was OK.
You see, his metabolism had apparently slowed down considerably so he didn't even feel hungry so late in the evening. Why was this a problem?
Well, when you're trying to grow your muscle, there are a few things you should keep in mind. For one thing, your body needs an increase in calories in order to have the raw materials to build that muscle. Where else is that muscle going to come from if it doesn't come from the raw ingredients in your diet.
(If you don't get enough carbohydrates, your body will use your muscle tissue as fuel.) Besides these points which you may already be familiar with, you need to have enough energy to allow for a solid muscle building workout.
If you consider why muscle grows in the first place, it's pretty easy to understand. You have to push your muscle to new heights, and this will stimulate your muscle to grow.
If you try to continue your workouts without getting the proper nutrition, you might be able to continue like this for a little while. However, if you're serious about muscle growth, take a long-term approach and start feeding your body properly.