I agree with NASM, it completely all depends but for the most part having a meal directly before working out is just fine. However, it all depends on the individual.......
The only time that I would say eating a large meal is bad is if the food you consume will cause your stomach to be upset during exercise. Then it will make your exercise less productive, causing less diminishing return and further away from the goals you are trying to accomplish.
It depends because some people genuinely prefer to workout on a empty stomach and others prefer to workout with food in the stomach. Working out is very placebo and very mental and if you feel good you will work out harder. That is one factor, the other factor is how much glucose is stored in your system. If you are in a depleted state and not much glucose is stored in your muscles then your workout will be less productive. So if in a depleted state a meal that is rich in carbs and protein directly before training can give you enough fuel to have a productive workout.
As I have said, it all depends. For myself personally I will have a light pre-workout energy drink and or sports drink and protein bar before training for just enough energy to have a productive workout. I think it cannot be disputed the importance of a large post workout meal to replenish carbohydrates and amino acids, vitamins and minerals lost during exercise. However, your post workout meal is like your pre workout meal, it all depends. It depends on how hard your workout is and the size of your body (or should I say relation between lean muscle and body fat).