One of the most important aspects of your nutritional program that you must consider if you want to see optimal gains is the pre and post workout period. This is the time when you really need to be sure you are eating optimally so that you are able to get the most results from your workout as well as have the energy that is necessary in order to give full effort. If you are not following a proper protocol, you likely will also not enjoy your training as much since it will feel more difficult (due to improper fuelling) nor will you recover as fast for your next workout session.

If you are dieting you likely will eat slightly differently before a workout than if you were trying to gain lean muscle mass, but the difference would mostly be in terms of total calories taken in, specifically with regards to carbohydrate intake.

For any exercise that is going to use the anaerobic system (sprinting or weight lifting), you will want a mixture of both carbohydrates and proteins in your pre workout meal. Carbohydrates are slightly less necessary in the post-workout meal if you are dieting however if there is room in your diet to include them, it is a good idea to do so.

On the other side of things, for a steady state, moderate intensity cardio session (or rather a moderate intensity sport), you could go with a simple protein drink before hand or skip it entirely provided you had eaten something within the last 3-4 hours during your day.

If fat loss is the goal, then you probably will want to skip a pre-workout cardio meal since it will help you burn more fat since you have no glucose present to burn off first.

The one macronutrient that should be avoided before a workout however, regardless of the type of activity you are going to perform is dietary fat. The reason for this is because it will slow the digestion process down and feel 'heavy' in your stomach, which is something that is not ideal for when you are exercising.

Do note however that this does depend on the time of the day in which you are eating. If like stated above you are only going to be doing a moderate intensity bout of exercise, you likely do not need to worry so much about eating right before hand.

In this case, fat may actually be a smart choice for right before a workout, particularly among those doing a low-carbohydrate diet. The reasoning for this is because when doing a low carbohydrate diet, particularly a ketogenic one, adding carbohydrates may take you out of ketosis, which is something you want to avoid. Since adding too much protein to a diet such as this can also cause you to come out of ketosis (since the excess protein will be converted to sugar in the body by a process called gluconeogensis), fat is really the only option left. As long as you are eating it a good one to three hours before the exercise session, there shouldn't be any issues (and again, this is referring to exercise that is of moderate intensity, not a high intensity interval cardio session or a heavy weight workout - those both call for carbohydrates before hand to prevent the loss of lean muscle tissue).

So next time you are getting ready for a workout, make sure your nutritional protocol is in line with your goals and the type of exercise session you are about to perform. Doing so can really make a difference in your performance and the results you see from your effort.