Muscle and other lean tissues are composed of protein. Thus, protein consumption provides structural support for the body. Most athletes are aware that protein in food and the body comprises smaller particles called amino acids, some of which can be manufactured by the body and others that must be ingested through food. To develop and maintain lean body mass, protein should be consumed regularly and in sufficient amounts.
The most concentrated sources of protein in food are found in animal products, such as meat, fish, fowl, eggs, and dairy. This can present a challenge to the vegetarian looking for adequate sources of dietary protein, but most plant foods contain at least small amounts of protein, too. For vegetarians who eat eggs and dairy products, consuming adequate protein is unlikely to be a problem. For vegans, it may be necessary to incorporate plant foods with high concentrations of protein (e.g., legumes or supplemental protein powder made from rice or hemp) into the diet.
Protein for Energy?
The role of protein for athletes is sometimes misunderstood. Some believe that a high-protein diet is important to “provide energy” for hard training and competition. In fact, protein is a poor substrate for providing energy; more than 90% of the energy for physical activity is produced through the metabolism of fat and carbohydrate. The chemical and mechanical process of converting amino acids to usable energy is time intensive and inefficient; thus, the body preferentially relies on other substrates to support energy demands during physical activity.
Amino acids are typically used as an energy source only when carbohydrate availability is limited during periods of starvation or extended moderate- to high-intensity activity.
For athletes, using protein as a fuel source is undesirable because the conversion process is too slow to support quick energy needs during training and competition. In addition, there is a finite supply of amino acids in the body, so fuel needed for extended and intense exercise would depend on the undesirable catabolic process of muscle breakdown or ingestion of amino acids during exercise.
Another misconception is that protein is needed in large quantities to support muscle maintenance and growth. This idea has likely been fueled by those who diet for aesthetic purposes, such as bodybuilders, fitness competitors, and models who may consume as much as 2 grams of protein per pound of body weight. To put this in perspective, consider a 200 lb. bodybuilder who attempts to eat 400g of protein a day. A typical chicken breast may consist of 50 grams of protein; thus, the equivalent of 8 chicken breasts would be eaten daily to meet these protein consumption goals. Even for athletes in hard training, this is excessive. For most, a daily intake of .75g to 1g/lb. will be more than sufficient.
Although high-protein diets are unnecessary for structural purposes, they can be advantageous for athletes who have a tendency to overeat. This is because protein is highly satisfying and unlikely to stimulate appetite the way foods with concentrated carbohydrate or fat might. Thus, perhaps the greatest benefit of a high-protein diet is its impact on eating behavior. Improvements in body composition associated with eating large amounts of protein may have more to do with the resulting reduction in total energy intake (i.e., amount of food eaten) than any specific effect of protein on body composition.
Take Home Message
- Protein consumption is necessary for maintaining and developing muscle mass. Animal foods are the most concentrated sources of protein.
- Protein is a poor source of energy for athletes; high-protein diets are not recommended for athletic performance.
- For most athletes, a daily protein intake of .75g to 1g/lb. is recommended.
- High-protein diets are highly satisfying, which may prevent overeating.