Nutrition for Physical Activity and Athletics
Being physically active has many health benefits, and good nutrition plays an important
role in physical activity and athletic performance. Whether participating in physical
activity for personal fitness or for competition, everyone benefits from a well balanced
diet following the USDA MyPlate Plan. The USDA MyPlate Plan encourages eating a variety
of foods from the USDA MyPlate food groups.
While the USDA MyPlate Plan provides the foundation for a healthy diet, there are
some special dietary considerations for physical activity and athletics.
Body Weight and Body Fat
Ideal body weight for health or athletic performance varies from person to person.
Age, gender, level of physical activity, and family history all affect body weight.
The importance of body weight goes beyond looks and physical performance.
For the general population, body fat levels between 18 percent to 21 percent for young men and 23 percent to 26 percent for young women are recommended. Trained athletes may have less body fat, ranging from 7 percent to 16 percent for men, and 15 percent to 22 percent for women. Body fat below 7 percent for men and 15 percent for women may also increase health risks.
Weight Management
Physical activity plays an important role in weight management. Physical activity
increases the number of calories the body uses, although the number of calories used
depends on the type, intensity, and duration of the activity. For substantial health
benefits, the Physical Activity Guidelines for Americans recommends adults engage
at least 150 to 300 minutes of moderate-intensity physical activity a week, or 75
to 150 minutes of vigorous-intensity physical activity, or an equivalent combination
of moderate and vigorous-intensity physical activity.
The goal for healthy weight loss is to lose body fat while maintaining lean body mass
and muscle. Weight loss should be gradual, 1/2 pound to two pounds per week, for both
athletes and non-athletes. Rapid weight loss increases loss of lean body mass and
muscle. There also is a higher risk of regaining weight lost rapidly. The best combination
for weight loss is a regular fitness program along with a well-balanced diet following
the USDA MyPlate Daily Checklist.
Weight loss may seem small at first when using a combination of diet and increased
physical activity, because muscle mass increases at the same time body fat decreases.
However, greater weight loss becomes apparent as body fat loss continues and muscle
gain levels off.
For athletes, the competitive season is not the time for either weight loss or weight
gain. The off-season is the time to adjust body weight so athletes enter their competitive
season at their optimal weight.
All weight loss techniques involving loss of body water are dangerous. Water loss
results in decreased blood volume and reduced blood flow to the kidneys, skin, and
muscles. This hinders the body’s ability to sweat and regulate body temperature, and
increases the risk of dehydration.
Carbohydrate
Carbohydrates are found in many foods including breads, cereals, grains, fruits, vegetables, and dairy foods. Carbohydrates should supply more than half of the calories consumed daily. A high carbohydrate diet increases muscle glycogen. Muscle glycogen provides an energy reserve for greater endurance and delays fatigue. Increased muscle glycogen is helpful for athletic events lasting longer than 90 minutes. Athletes may use a modified carbohydrate loading plan to increase muscle glycogen. This plan involves reducing workouts the week before an event and complete rest the day before an event. Along with reduced workouts, the athlete begins eating a high carbohydrate diet three days before the event.
Protein
Protein is found in many foods including meat, poultry, fish, eggs, nuts, milk, yogurt,
cheese, beans, peas and lentils. The Dietary Reference Intake for protein for healthy
adults is 0.8 grams protein per kilogram body weight. Competitive athletes sometimes
need one to one and a half grams of protein per kilogram body weight. This higher
amount of protein can easily be obtained from a well-balanced diet with a variety
of foods.
The increased need for protein does not mean athletes need amino acid or protein supplements.
There is no evidence that amino acid or protein supplements increase muscle mass.
In fact, excessive amino acid or protein supplements can be harmful. Products from
protein breakdown are excreted in the urine increasing water loss and risk of dehydration.
Fat
Carbohydrates and protein provide most of the daily calorie needs. Fat is used for the remaining calories. For good health, the Dietary Reference Intakes (DRI) recommend a diet low in saturated fat and trans fat, and one which provides 20 to 35 percent of the daily calories intake from fat.
Vitamins and Minerals
Vitamins and minerals have important roles in carbohydrate, protein, and fat metabolism.
Without vitamins and minerals there would be no muscle function. Physical activity
increases the need for some vitamins and minerals. A well-balanced diet will supply
enough vitamins and minerals to cover any increased need due to activity. There is
no evidence that athletes need extra vitamins and minerals if they consume a well-balanced
diet. There is also no evidence that vitamin and mineral supplements improve athletic
performance.
Iron is a mineral that is very important for both physically active women and young
athletes. Iron is part of hemoglobin, the protein that carries oxygen from the lungs
to the muscles. “Sports anemia” is a condition that sometimes occurs in athletes due
to increased blood volume associated with initial training. This condition is usually
temporary and does not affect athletic performance. However, iron deficiency can lead
to fatigue and hinder athletic performance. Red meat is a rich source of iron that
is easily absorbed by the body. Fortified breads and cereals and green, leafy vegetables,
such as broccoli and spinach, also provide iron. However, iron from plant foods is
not as easily absorbed as iron from animal sources by the body. Increase the absorption
of iron from plant foods by eating them in combination with animal sources or foods
rich in vitamin C, such as orange or tomato juice.
Calcium is also a mineral that is very important for physically active women and young
athletes. Low body fat levels and high physical activity may hinder bone development
in young female athletes. Adolescence and early adulthood is a time when maximum bone
formation occurs. Decreased bone development can increase the risk of stress fractures
and hurt athletic performance. It is important that all athletes, especially young
female athletes, consume adequate dairy products such as milk, yogurt, and cheese
for calcium. Calcium is also found in dark-green leafy vegetables, fortified breads
and cereals, and calcium fortified orange juice.
Fluids
Physical activity results in increased heat production in the body. The main way the
body removes heat is by sweating. Water loss from sweating can decrease muscle strength,
endurance, coordination, and increase risk of cramps. Excessive body water loss can
result in heat exhaustion and heat stroke, which can lead to death.
Replacing water lost by sweating is the best way to prevent dehydration. Thirst is
not a good indicator of water need. Weighing before and after physical activity is
an easy way to determine the amount of body water lost through sweat. It requires
one pint (2 cups) of fluid to replace each pound of body water lost in physical activity.
Guidelines for fluid intake before athletic events include drinking extra water for
several days before an event in order to start the event well hydrated. Guidelines
for fluid intake during athletic events are two cups to three cups of fluid, two hours
to three hours before the event; and one to two additional cups of fluid, 15 to 20
minutes before the event. Small (1/2 cup) servings of plain cool water should be consumed
frequently throughout the event.
For most individuals exercising less than one hour, cool water is the best way to
replace fluids. The typical American diet provides enough sodium and other minerals
to replace those lost through sweat. Sports drinks may be useful when exercising over
one hour or in high temperature or humidity conditions. The body easily absorbs sports
drinks containing six to eight percent glucose or sucrose with a small amount of sodium.
These drinks help maintain blood glucose, without causing stomach cramps. Concentrated
sports drinks, or sports drinks containing fructose, may cause stomach cramps.
Ergogenic Products
Ergogenic products claim to provide energy, improve strength or endurance, or improve athletic performance. Examples of ergogenic products include: bee pollen, caffeine, glycine, carnitine, lecithin, brewer’s yeast, gelatin, amino acids, protein supplements, and vitamin/mineral supplements. There is no scientific evidence that ergogenic aids improve athletic performance. These products may hinder both health and athletic ability when they replace sound dietary practices.
Dietary Recommendations for Exercise or Competition
Before Exercise or Competition: Food eaten before exercise or competition can help
prevent low blood sugar, provide energy, and settle the stomach. However, what to
eat before exercise or competition varies from person to person and from activity
to activity. Some people can eat almost anything, while others have no desire to eat
anything.
High carbohydrate foods can help maintain blood sugar levels. Some examples of high
carbohydrate foods include yogurt, bananas, pasta, crackers, bread, or bagels. Some
people can tolerate small amounts of sugary foods just before events; however, for
others these types of foods can cause a drop in blood sugar.
Foods that cause stomach or intestinal problems such as high fat, high protein, or
fiber should be avoided. Some can tolerate a liquid meal that provides a good balance
of fluid and nutrients better than food.
Allow enough time for food to digest. A general rule is to allow at least three to
four hours for a large meal to digest, two to three hours for a smaller meal, one
to two hours for a liquid meal, and less than an hour for a small snack.
What and when to eat should be tested before a competition. Don’t try new routines
the day of a competition.
During Exercise or Competition: For events lasting less than 60 minutes, consuming
carbohydrate during the event is not usually helpful. For events lasting longer than
60 to 90 minutes, consuming small amounts of fluid and small amounts of carbohydrate
(0.5 grams carbohydrate per pound body weight) every hour may delay fatigue. The type
of carbohydrate tolerated will vary from person to person. Some people can tolerate
carbohydrate-containing foods while others can better tolerate carbohydrate-containing
beverages. Try this during practice. Do not try consuming carbohydrates for the first
time during a competition.
After Exercise or Competition: The top dietary priority is to replace fluids lost
through perspiration. Consuming a small amount of food or beverage high in carbohydrate
and low in fat, fiber, and protein within 15 minutes of exercise or competition helps
to replace muscle glycogen stores. The type of carbohydrate tolerated after exercise
or competition will vary for each person.
Summary
Nutrition is an important factor affecting fitness and athletic performance. Whether one participates in physical activity for personal fitness or for competition, the best nutritional recommendations are to consume adequate fluids and a well-balanced diet from a variety of foods following the USDA MyPlate Plan.
References
Whitney, E.N. & Rolfes, S.R. (2015). Understanding Nutrition, 14th ed., Wadsworth,
Cengage Learning, Belmont, CA.
Brown, J.E. (2014) Nutrition through the Life Cycle, 5th ed., Cengage Learning, Stamford,
CT.
United States Department of Agriculture. ChooseMyPlate.gov. Accessed at www.choosemyplate.gov
United States Department of Health and Human Services. 2018. Physical Activity Guidelines For Americans. 2nd ed.
Janice R. Hermann, Ph.D., RD/LD
Nutrition Specialist