Each gram of protein provides four calories. The word "protein" comes from a Greek word meaning "first" or "of primary importance." For bodybuilders and strength athletes, this nutrient is of primary importance, because proteins are the building blocks of, among other things, muscle tissue. Protein is broken down into amino acids in the body, and these amino acids are turned into muscle via a process called protein synthesis, or muscular anabolism (from another Greek word meaning "to build up" or "ascend."
Proteins (amino acids) make up the major portion of the solid part of a muscle. Around 20-25% of the muscle content is protein, 70% is water and other fluids, and the remaining 5-10% comprise muscle glycogen, minerals, intramuscular fatty acids and other elements. You don't need to memorize the proportions, just master the point that protein is the most important nutrient for muscular growth. No protein, no muscle.
Exactly how much protein is needed for maximum growth? Good question. Studies have shown over and over that a higher protein intake is associated with a more positive nitrogen balance and a higher rate of protein synthesis. In other words, the more protein you eat, the more muscle you build.
However, it's not that simple. At some point we run smack into the law of diminishing returns. Once you've reached the maximal amount of protein that your body can use to build muscle, any additional protein you swallow will notincrease your rate of muscular growth.
That sucks, doesn't it? I mean, wouldn't it be great if all we had to do to build muscle was consume tons of protein? In no time at all, we'd all be 250-pound shredded behemoths! Even the girls! Sadly, we are limited by our own natural biochemistry when it comes to being able to use protein (amino acids) to build muscle.
Protein is found primarily in animal products such meat, poultry, fish, shellfish, eggs, milk and cheese.