If you're an exerciser, however, your protein needs may increase since resistance training and endurance workouts can rapidly break down muscle protein. A position statement published by the ADA, DOC and ACSM recommends that endurance and strength-trained athletes have between 1.2 and 1.7 g/kg (0.5 - 0.8 grams per pound) of protein for the best performance and health.
What if you're trying to build more muscle? Shouldn't you eat even more protein? Not necessarily. There's evidence that bodybuilders, much like exercisers or athletes, do require more protein but that any more than double the RDA won't necessarily help you build more muscle. In one study, experts studied three groups of weight lifters: A low protein group (0.86 g/kg), a moderate protein group (1.40 g/kg) and a high protein group (2.40 g/kg) and found that, "There were no effects of varying protein intake on indexes of lean body mass."
In essence, the more you exercise, the greater your protein needs will be. However, taking it too far, for example more than doubling your protein intake, won't necessarily help you build more muscle.
How to Calculate Your Protein Needs:
1. Weight in pounds divided by 2.2 = weight in kg
2. Weight in kg x 0.8-1.8 gm/kg = protein gm.
Use a lower number if you are in good health and are sedentary (i.e., 0.8). Use a higher number (between 1 and 1.8) if you are under stress, are pregnant, are recovering from an illness, or if you are involved in consistent and intense weight or endurance training.
Example: 154 lb male who is a regular exerciser and lifts
154 lbs/2.2 = 70kg
70kg x 1.5 = 105 gm protein/day
Calculating Protein as a Percentage of Total Calories
Another way to calculate how much protein you need is by using daily calorie intake and the percentage of calories that will come from protein. To do this, you'll need to know how many calories your body needs each day.
Next, figure out how many calories you burn through daily activity and add that number to your BMR. This gives you an estimate of how many calories you need to maintain your current weight.
After you've figured out your maintenance calories, next figure out what percentage of your diet will come from protein. The percentage you choose will be based on your goals, fitness level, age, body type and metabolic rate. Most experts recommend that your protein intake be somewhere between 15 and 30%. When you've determined your desired percentage of protein, multiply that percentage by the total number of calories for the day.
For a 140lb female, calorie intake=1800 calories, protein=20%:
1800 x .20 = 360 calories from protein. Since 1 gram of protein = 4 calories, divide protein calories by four:
360/4 = 90 grams of protein per day.
No matter what your calculations are, remember that there are no magic foods or supplements that can replace the right training and the right diet. The foundation of any program, whether your goal is to lose weight or gain muscle, is a combination of strength training and a healthy diet that includes carbs, with a balance of protein and fat.
American Heart Association. "High-Protein Diets." Accessed: Sept 22, 2009. http://www.heart.org/HEARTORG/GettingHealthy/NutritionCenter/High-Protein-Diets_UCM_305989_Article.jsp
DietaryFiberFood.com. RDA: Protein Requirement for Humans. Accessed: Sept 22, 2009. http://www.dietaryfiberfood.com/protein-requirement.php.
Lemon, P. Beyond the Zone: Protein Needs of Active Individuals. J Am Coll Nut, 2000; 19(90005): 513S-521S.
Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Diet Assoc. 2009 Mar;109(3):509-27.
Tarnopolsky, MA; Atkinson, SA; MacDougall, JD; et al. Evaluation of protein requirements for trained strength athletes. J Appl Physiol. 1992 Nov;73(5):1986-95.