You definitely need to be eating a meal before a workout, giving yourself an hour or so to digest. Something with some complex carbs and protein, oats blended in a protein shake are great for me. After workout, you need protein to get into your system to start feeding the hungry, damaged muscles. You also need more carbs to restore energy, dextrose is great since it can get broken down and absorbed quickly...
Not eating before a workout is a bad idea, same as not getting nutrients after one...lots of water before and after too...