Protein is the building block of muscles and essential for repair and growth of muscle after exercise. Whenever you exercise, and particularly during resistance exercise, you cause microscopic damage to the myofibrils of muscle fiber (myofibrils are small protein filaments in the muscle fiber that help the muscle contract). This isn't the type of damage that you go to the doctor for, but normal biological damage called catabolism. The effect creates a stimulus and environment for muscle repair and growth. The body responds to the damage by sending nutrients, including protein and other growth factors like testosterone, to the muscle to help it grow. Contrary to what many people think, protein is not used by the muscles for fuel unless the circumstances are extreme (for example, starvation). Instead, fat and carbohydrate are the main fuels.

Research shows that protein consumed before exercise and within 30 minutes of finishing your workout will help with growth and recovery. The guideline for protein consumption after exercise is 1 gram for every 3-4 grams of carbohydrate. Peanut butter has 9 grams of protein per 2 tablespoons. Yogurt is another good source of protein. The guidelines for quantity of protein before exercise are not as clear as after, but you can experiment and see if you notice any difference.

You probably won't notice much difference using protein supplements unless you are malnourished or an elite athlete doing tremendous amounts of aerobic or resistance exercise. That's because most Americans, including athletes, get enough protein in their diets. Excess protein is not used by the body; instead, it is excreted in urine. Discuss your recommend protein intake with a doctor or registered dietitian.

Here's one way to calculate your protein needs:

1. Divide your weight by 2.2 to calculate your weight in kilograms.
2. Multiply your weight in kilograms by 0.8-1.7 gm/kg (depending on factors mentioned above).

Here's an example if you weigh 200 pounds and consistently do heavy resistance exercise:

200/2.2 = 91 kg
91 kg x 1.4 = 127 grams of protein per day

Again, keep in mind that most Americans get enough protein in their diets.

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