Nutrition is a crucial component of sports training. However, it is often not given much thought. What is important to understand is that all the intelligent, advanced training in the world is completely useless if the body does not respond to it. It is during recovery time that gains are made. The training only provides the stimulus. The body has to adapt to it. The food you consume is what your body must use to respond to this stress. So nutrition is extremely vital to the recovery process and thus vital to sports training. Nutrition does not have to be complicated, but many people are uneducated on the subject. This article is meant to cover the basics.
All food is made of some combination of carbohydrates, protein, and fat. These are the three macronutrients. Carbs are the most efficient source of energy. If unused, carbohydrates can be stored as fat. Protein can also be used for energy, but it primarily serves as the material used to build or repair all the structures in the human body. Fat is also used for energy; it actually contains more than twice as many calories as carbs or protein and thus requires more activity to burn. There are other uses for fat as well.
There are some basic guidelines to follow for sports nutrition. First, make sure you get enough carbohydrates to fuel your body through all the activity that you do. Your muscles' preferred fuel is a substance called glycogen, which is formed from carbohydrates. If glycogen stores are depleted, the body will turn to other sources of energy, namely fat and protein. The first problem with this is these energy sources are not as efficient. More importantly, the source of the protein that your body will burn is skeletal muscle. That's right. Your body will burn muscle fiber for energy when it's short on carbohydrates. This is called a catabolic, or muscle-wasting hormonal state. Many people fail to adequately maintain their glycogen supply; I believe this is one of the leading causes for lack of success in training. The hardest part of becoming an advanced athlete for many people is sustaining strength gains beyond the first few months of lifting. I believe one of the primary reasons is people do not adequately fuel their bodies throughout the day and for all the exercise they do. You end up with a strong strengthening stimulus from lifting and a hormonal environment in the body that does not allow for a positive response. If you look at powerlifters, the guys who compete in the squat, deadlift, and bench press, most of them are not very lean despite having loads of calorie-burning muscle mass. That's because they eat a ton of food in order to keep their body in an anabolic, or muscle-building hormonal state. The point is YOU GOTTA EAT. When your body is hungry, it's hungry for a reason. You have to feed the machine. Going hungry is a big mistake.
Controlling the environment inside your body is equally important in gaining strength as the actual workouts. Consider an adolescent male; his body is just dripping with testosterone. Consequently, just about any workout strategy he employs will result in drastic strength gains. So instead of worrying about finding the perfect workout program, just use something decent and focus on making your body chemistry more like that of the adolescent male. Once you're full grown you don't have the luxury of super high testosterone levels. That's when nutrition becomes much more important in manipulating body chemistry.
My second guideline is make sure you supply your body with enough protein to recover from all the training you do as well as maintain regular body function and repair. This is especially important if you are trying to build muscle. There are a lot of alleged rules for how much protein athletes should consume. Unfortunately the rules vary from recommending 1 gram per pound of body weight each day to recommending less than half that. So no one really knows. In my experience the people recommending a lot of protein are the people selling protein supplements. 1 gram per pound of body weight is a pretty extreme recommendation. However, a diet that is a little high in protein is not the worst thing, as long as there is a good supply of fruits and vegetables accompanying the protein. So feel free to err on the side of caution and eat a lot of protein. Try to include it in each meal. There is no need to load up on protein specifically after a workout. (Just for the record, the risk of protein dominating your nutrition is an internal environment that is too acidic. To neutralize the acidity, the body has to take calcium from the bones. Over time, this can lead to low bone density. Bone density is not typically an issue for athletes... but there was that Kevin Ware thing...)
As far as fat, with the food industry of today, if you are getting enough carbs and protein, the fat will come with it. So don't worry about getting enough fat. Instead concern yourself with what kind of fat you consume. Natural, unsaturated fat is healthy for your body. Saturated fat is not. Healthy fat is found pretty exclusively in eggs, nuts, seeds, and meat.
So how much do you need to eat? You could go through all kinds of calorie counting and calculations of your metabolism to try to find the right amount of food to eat, but there is a simpler way. Just eat when your body tells you to eat, eat as much as you need, include both carbs and protein, and try to get your carbs and protein from the healthiest sources possible. This will keep your body healthy and prevent you from consuming excessive amounts of unhealthy fat. Fruits, vegetables, nuts, seeds, and beans, are your best options. Fish, Eggs, milk, meat, pasta, and cereal are the next best choices. Try to eat things that are as close to their natural state as possible. Further processed food is less healthy food. If you stick with primarily healthy food, you can eat sufficiently rather than go hungry and not gain unwanted body fat. If you do that along with consistent full body training, you should gain a very lean body over time.