The UCSF-John Muir Health Jean and Ken Hofmann Cancer Center at the Behring Pavilion is now open. LEARN MORE >
Balancing exercise and nutrition is important in keeping fit. When you exercise, you need to be sure to get all the nutrition your body requires to keep it moving.
A calorie represents how much energy you get from food. The amount of calories you need to eat every day varies depending on your weight, your age, your gender, and how active you are.
The more exercise you get, the more calories you need to eat to maintain your weight. Depending on your training program, exercise can increase your calorie needs by 1,000 or 1,500 calories a day. The best way to judge if you’re getting too few or too many calories is to monitor your weight.
Fats and carbohydrates are main sources of fuel for your body. For short-term, high-intensity sports like sprinting, your body uses mostly carbohydrates for energy. For long duration, low- to moderate-intensity endurance activities like cycling, walking, or jogging, your body uses more fat for energy.
Carbohydrates are the sugars and starches that come from foods such as bread, cereal, fruits, vegetables, milk, and pasta. Your body converts carbohydrates into glucose and uses it for energy.
When training and competing in athletics, your muscles need energy for peak performance. Glycogen is a source of energy for your muscles and comes from the carbohydrates your muscles store.
Fat has more than double the calories of carbohydrates. Less than 30% of your daily calories should consist of fat calories and more than half your daily calories should come from carbohydrates.
It’s a myth that eating extra protein or taking protein supplements in combination with exercise will give you bigger, stronger muscles. Muscle strength depends mostly on genes, how hard you train, and consuming the calories your body needs to build muscle. To maximize strength and performance, 10-15% of your daily caloric intake should come from protein.
Athletes need to eat about 1,800 calories daily to get the vitamins and minerals they need for peak performance. Eating a diet rich in a variety of different fruits, vegetables, whole grains, and dairy products will likely give you all the vitamins and minerals you need.
Most athletes get more vitamins and minerals than they need every day and don’t need to take supplements. Since vitamins and minerals don’t give you energy, it’s best to get them through the food you eat to ensure you are also eating enough carbohydrates.
Vegetarian athletes and athletes who have dietary restrictions (like not drinking milk), may need a supplement to make up for the vitamins and minerals they don’t get in food.
Hemoglobin contains iron and makes up part of the red blood cells that supply muscles with oxygen to keep them working. Without enough iron, you may tire easily, lose stamina, and feel fatigued, irritable, dizzy, or have headaches.
Athletes should have their iron levels checked with a blood test once a year. If you are iron deficient, you should talk to your doctor about ways to boost your iron consumption.
The recommended daily intake (RDI) of iron is 18 milligrams per day for women under 50 years old. For men and women over 50 years old it drops to 8 milligrams per day. Red meat is the richest source of iron. Fish, chicken, fortified cereals, beans, and green, leafy vegetables are also good sources.
Iron supplements will not boost your performance unless you are iron deficient. Iron supplements can cause side effects such as constipation and diarrhea, so it’s best to consult with your doctor first before taking them.
Calcium builds strong bones and helps muscles function properly. Many female athletes don’t get enough calcium and may be at risk for stress fractures or for osteoporosis (a bone disease mostly found in older women).
Dairy products are the best source of calcium. Salmon with bones, sardines, collard greens, and calcium-fortified foods such as tofu or orange juice are also good sources.
Young men and women between the ages of 11 and 18 need about 1300 milligrams of calcium a day. The recommended daily intake for adults is 1000 to 1200 millligram of calcium per day depending on gender and age.
Water is the most important nutrient for athletes. Maintaining your body’s fluid level is important because when you exercise, you sweat and lose water. To maintain athletic performance, you need to make sure you drink fluids before, during, and after all your workouts and athletic events.
If your workouts are long (60 minutes or more), you may benefit from drinking a sports drink. Sports drinks contain a combination of carbohydrates and electrolytes. They replace fluid and electrolyte losses and provide energy needed to sustain your activity level.
Look for a sports drink that contains 15-18 grams of carbohydrate in every 8 ounces of fluid. More than that will slow down your absorption of water and can cause side effects like dehydration.