People ask me all the time "what should I be eating before and after I exercise?" This can be a fairly complex question and is dependent on a bunch of different variables. Your goals, weight, type of exercises you do, gender, age, and dietary restrictions will all affect what you should be eating before and after as well as what the major nutrients are and the roles they play.
The three essential nutrients in discussion are proteins, carbohydrates and fats. Each one is used for fuel with carbohydrates being used the most and proteins the least. Carbs and fats are the two main forms of fuel for the body, but each applies to different situations. Carbohydrates are the primary fuel used by the body for both short duration, high intensity exercise (i.e. sprinting, weight lifting and jumping) as well as long duration exercise (i.e. marathon runs). It is also the main source of energy for the brain.
Fats are the primary energy source for long duration, low intensity exercise (i.e. day long hike) and they also can be burned throughout the day as a fuel source. Because of this, the type of exercise you are participating in will dictate what form of fuel your body is going to need. It is also important to remember that it is not one or the other; both fats and carbohydrates are used during activity and throughout the day, just in varying amounts.
The last of the three nutrients being discussed, are proteins. While proteins are used for fuel (very little), they are essential for the repair of muscles as well as muscle contraction. When you exercise, your muscles get little micro tears in them from the activity. Protein, the building blocks of muscles, is what works to repair these micro tears. For this reason, eating protein after strenuous activity or a workout is very effective in getting stronger and repairing your muscles faster.
For myself, I am a 32 year old female that engages in moderate to high levels of activity 1-2 hours a day, 5 times a week (on average). Taking those and other variables into consideration, I would have a piece of fruit right before, probably a banana, and a tuna sandwich right after. The banana is a carbohydrate (fuel) that is high in potassium (aids in muscle contraction) and the tuna sandwich will provide my protein (muscle repair), as well as carbohydrates to replenish what fuel was used during the workout. I prefer to eat small amounts before a workout (just a banana) as my body responds better than if I had a larger meal. Again, this is taking MY requirements and variables into account.
It is important to note that what was discussed here is a brief overview of these nutrients and the roles they play. Also to note is that your nutrition is extremely important and is a major component in your health. It is just as crucial as exercise. It is in your best interest to educate yourself on what you are eating and how it effects your body. This education can come in the form of on-line research and courses (scholarly articles and reputable sources only please) as well as consulting a professional such as a dietician or nutritionist who can advise you properly.
At the end of the day knowledge is power. Make sure you know what your body needs and when it needs it because your insides are just an important as your outsides.
For a reputable site with great nutritional information, you can visit Lindsay Jang's (Registered Dietician) at www.lindsayjang.com.