Chapter 15Nutrition for Fitness

and Athletics

Focus on nutrition• Sports nutrition is an area in which fads

often obscure scientifically valid information.

• Performance can deteriorate rapidly if diet is less than optimal

• The best diet for one athlete may not be the best for another.

Visit:Nutrition Navigator at http://navigator.tufts.eduFood and Nutrition Information Center at www.nal.usda.gov/fnic/American Dietetic Association at www.eatright.org

Typical diet vs. recommended diet

Typical:• Carbohydrate

– 46%• Protein

– 12%• Fat

– 42%

Recommended:• Carbohydrate

– 55 to 58%• Protein

– 12 to 15%• Fat

– 25 to 30%

Recommended caloric intake for healthy persons in the United States

Caloric intake for athletes• Athletes in heavy training often

consume 4000 to 7000 calories a day.• If athletes eat less than they need to

meet their energy demands, they will burn body tissues to make up the deficit.

Carbohydrates• Contribute to energy production in exercise in

the form of blood glucose and stored muscle glycogen

• Manipulation of carbohydrate intake and exercise can result in larger than normal store of muscle glycogen and increased endurance

• Fat produces more than twice as much energy per gram, but requires more oxygen for each calorie. Carbs offer an advantage of about 7.5%.

Simple and complex carbohydrates

• Complex carbohydrates—combination of three or more glucose molecules

• Simple carbohydrates—one or two sugar molecules joined together– Monosaccharides—glucose, fructose,

galactose– Disaccharides—sucrose, lactose, maltose

• Only 10% of total caloric intake should come from simple sugars

Recommended carbohydrate intake before, during, and after a competition

• Before– should be based on the athlete’s experiments

during training• During

– take in 25 to 30 grams of carbohydrate (100 to 200 kilocalories) every half hour

• After– take in 100 grams of carbohydrate (400

kilocalories) within 15 to 30 minutes of exercise and additional 100-gram feeding every two to four hours thereafter

Factors that affect protein metabolism during exercise

– Mode of exercise– Frequency of exercise– Intensity of exercise– Duration of exercise– Training status– Quality of protein

Fat intake

• At beginning of exercise, circulating level of free fatty acids decreases.

• After a few minutes of continuous exercise, fatty acids stored in adipose tissue mobilize, increasing circulation of free fatty acids.

• Endurance training improves ability to metabolize fats.

• Enhanced ability to metabolize fats during submaximal exercise may result in sparing of carbohydrate stores and thus increase duration of activity.

Vitamin supplements

• If the diet is sound, supplementary vitamins are not needed. Eating larger amounts of food as daily workout levels increase usually provides the needed increase in vitamins.

Visit Vitamins and Minerals at www.foundhealth.com/vitamins

Iron deficiency• Sports anemia is anemia that occurs in

response to heavy endurance training • Three stages of iron deficiency

1. Prelatent iron deficiency2. Latent iron deficiency3. Frank anemia

Iron supplements• A diet high in iron sources should prevent iron

deficiency, but the following may require supplementation:– Male and female endurance athletes– Adolescent athletes– Athletes who lose weight for competition– Vegetarian athletes

• Never give iron supplements without medical supervision– Can induce deficiencies of trace minerals– Can produce an iron overload (hemochromatosis)

The American College of Sports Medicine’s recommendations regarding fluid intake before, during, and after exercise.

1. Drink adequate fluids during the 24-hours before an event.

2. Drink about 17 ounces about two hours before exercise.3. During exercise, consume enough fluids to replace water

lost through sweating.4. Fluids should be cooler than ambient temperature,

flavored, and in containers that make it easy to drink enough without disrupting exercise.

5. For events lasting over an hour, fluids should contain proper amounts of carbohydrates and electrolytes.

6. During intense exercise lasting more than one hour, drink fluids containing 4 to 8 percent carbohydrates.

7. For exercise lasting more than an hour, sodium should be included in the rehydration fluid.

Desired characteristics of pre-exercise meals

• Have sufficient fluid to maintain hydration

• Be low in fat and fiber • Be high in carbohydrate• Be moderate in protein• Be composed of food familiar to the

athlete