Your body requires optimal nutrition to meet the demands placed on it by regular exercise.  Adequate amounts of carbohydrate, protein and fat are needed not only to fuel the activity but to repair and rebuild muscle tissue that has been broken down from exercising.  If energy and nutrient intake are insufficient, your exercise performance can be hindered, injury and illness could result and the health benefits of the exercise can be minimized.  

     Many active individuals wonder how many calories they need daily to "drive" their exercise.  Regular exercisers need more calories per day than their less active counterparts in order to maintain energy balance.  Energy balance occurs when the amount of calories consumed equals the amount of calories burned throughout the day.  Energy requirements are based on gender, age, body size, nutritional status, amount of activity involved in daily tasks, exercise mode, and intensity level, duration, and frequency of exercise.  Sports nutritionists use predictive equations to determine total energy expenditure and thus calories needed on a daily basis.  To determine your caloric needs refer to the United State's Department of Agriculture's (USDA) Nutrition and Your Health: Dietary Guidelines for Americans section of their website at www.health.gov/dietaryguidelines/dga2005/report/HTML/D3_Disccalories.htm and go to the subheading "Calculating the Estimated Energy Requirements".

     In addition to knowing the total number of calories needed daily, active individuals want to know what is the best energy source to fuel their exercise.  The contribution of fuel sources is dependent upon the intensity and duration of the exercise as well as your fitness and nutritional status.  According to the President's Council on Physical Fitness and Sports Research Digest March 2004, the amount of carbohydrate needed for moderate intensity exercise is 5-7 grams/kilogram of body weight and 7-12 grams/kilogram of body weight for high intensity endurance exercise.  Protein requirements for the active individual (including those involved in resistance training) range from 1.2-1.7 grams/kilogram of body weight or 15% of total daily calories consumed.  Fat intake should range from 20-35% of total daily caloric intake (or 1 gram/kilogram of body weight according to recommendations outlined in the ACSM Fit Society Page Winter 2007) with carbohydrate and protein needs taking precedence over fat consumption.  In the American College of Sports Medicine Position Stand on Nutrition and Athletic Performance they advise against following diets that severely restrict calories or ones that exclude/eliminate certain macronutrients (e.g. carbohydrates) because of the negative effects on health and performance.  

     Carbohydrates are needed by your body because they are its primary energy source.  They maintain blood sugar levels during the activity as well as replenish sugar stores (glycogen) that have been depleted from the exercise.  According to the ACSM Position Stand, 50-60% of the energy needed to sustain 1-4 hours of continuous exercise at 70% of maximal capacity comes from carbohydrates.  Adequate amounts of carbohydrates are also needed to spare amino acids for protein synthesis (muscle tissue repair/building).  Insufficient amounts could lead to amino acids being used to meet the energy demands of the exercise instead of muscle repair, resulting in decreased muscle mass.  Good sources of carbohydrates include whole grain pasta, bread and cereals (oatmeal), brown rice, potatoes, and fruit.

     Protein is needed by your body to repair and build muscle and connective tissue.  Although active individuals need more protein than their sedentary counterparts, the difference is not enough to warrant protein supplements according to recommendations outlined in the ACSM Fit Society Page Winter 2007.  Eating too much protein can lead to the body converting and storing the excess into fat.  Good sources of protein include lean meats, low- or non-fat dairy products, fish, eggs, soy products, beans, and legumes.

     Fat is a valuable energy source for activities lasting longer than 3 hours.  Saturated fat sources, such as from animal products, should be limited because of their role in the development of heart disease.  Good sources of "healthy" fats (unsaturated fats) include fish, nuts, avocados, olive oil, and soy products.

     Acquiring proper nutrition and meeting your body's energy requirements is a balancing act.  Adjustments may be needed as your fitness level and exercise routine changes.  Age will also impact your energy requirements, with a decrease in total caloric needs occurring as you get older.  Monitoring the amount and type of calories that you consume will enhance your exercise performance as well as your overall health.

Note:  Before beginning an exercise program or increasing the intensity level of a current routine, a physician's approval should be obtained, especially for older adults and those at risk for or who currently have chronic health conditions.

Resources:

United States Department of Agriculture Food and Nutrition Information Center "Nutrition and Your Health: Dietary Guidelines for Americans" (www.usda.gov)

President's Council on Physical Fitness and Sports Research Digest. Series 5, No. 1; March 2004 (www.fitness.gov)

American College of Sports Medicine ACSM Fit Society Page Winter 2007. "Nutrition: Who needs it?  If you're and athlete... you do!" pp.5-6, LeBlond, J., Beals, K.

American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada Joint Position Statement "Nutrition and Athletic Performance" Medicine & Science in Sports & Exercise, pp. 709-731,