Athletes may need to follow a different diet than non-athletes. A diet is composed of multiple parts; macronutrients such as carbohydrates, protein, and fat, and micronutrients such as vitamins and minerals. Recommendations for these components may change depending on age, gender and sports participation. Energy for sports participation comes from carbohydrates, protein and fat, of which carbohydrates should account for at least 50% of daily intake. Fat intake should be 20-25% of the total calorie intake, and protein should account for 10-15% of calorie intake.(1, 2, 3, 4, 5, 6, 7)

Protein:

Why is protein important?

Protein is required for hormone and enzyme production, nutrient transfer in the blood, connective tissue support and repair of tissue in response from exercise.

How do I get bigger muscles?

Hypertrophy is a slow process from resistance exercises where the muscle fiber changes and increases in diameter, this takes repeated stimulus (resistance exercise) and at least 6-8 weeks to see outward changes. (8)

Hypertrophy (muscle enlargement) is the result of the accumulation of successive periods of positive protein balance after exercise when protein is consumed. This means that more protein is consumed after exercise, then broken down during exercise, creating more protein to repair muscle tissue. Resistance exercise stimulates an increase in the rate of muscle protein.

Do I need a protein supplement?

No. Protein needs for all athletes can be met by diet alone and should not require supplementation. If protein intake is too high, it can produce extra urea, increase risk of dehydration and calcium loss.(1,8)

When should I consume protein after exercise?

After exercise, protein plus carbohydrates should be consumed within the first hour as studies have shown that consumption after 2 hours provided less hypertrophy and less strength gains. (8) Although more studies are needed on this subject.

Carbohydrates:

Why are carbohydrates important?

Carbohydrates are the primary fuel for sport. (2) They are important to maintain blood glucose levels during exercise and to replace muscle glycogen (the storage form of carbohydrates in the muscle that gets converted into glucose for use). Carbohydrates contribute to the energy pool that athletes use during exercise. (6)

When should I consume carbohydrates?

Before exercise as a snack that is predominately carbohydrate, low in fat and fiber and moderate in protein. (6) During exercise at a rate of about 30-60 grams per hour, and after exercise 1.5g/kg body weight within 30min and again every 2 hours for the first 4-6 hours along with protein for muscle building and muscle repair. (6)

Fat:

Why is fat important?

Fat provides energy to athletes, and may be the preferred fuel source for child athletes (2,6). There is no benefit to athletes when fat intake is less than 15% or greater than 30% (1).

Child/Adolescent Nutrition Guides for Athletes (2,3):

Age/sex Daily Calories Daily Calcium Intake Daily Protein Intakes Daily Essential Fatty Acids Intake
4-8, boys and girls 1,400-1600 1300mg 19grams
9-13, boys 1,800-2200 1300mg .77gram/kg or 34grams 12grams
9-13, girls 1,600-2200 1300mg .73gram/kg or 34grams 10grams
14-18, boys 2,200-2600 1300mg .75 gram/kg or 52grams 16grams
14-18, girls 2000 1300mg .73grams/kg or 46grams 11grams

Child/Adolescent Carbohydrate and Protein Calculations (2):

Carbohydrate

Training Intensity Calculation
Light training (2-3 times per week) 1.5-2.5 g/lb body weight
Moderate training (3-5 times per week) 2.5-4 g/lb body weight
Pre-event load 4-4.5 g/lb body weight
Post-event refuel 0.8 g/lb body weight
Training Intensity Weight Carbohydrate Intake
lbs grams per day

Protein

Activity Intensity Calculation
Training 0.5-0.7 g/lb body weight
Endurance 0.5-0.8 g/lb body weight
Strength Training 0.5-0.8 g/lb body weight
Athletes who are calorie restricting 0.8-0.9 g/lb body weight
*Maximal Usable Protein 0.9-1.0 g/lb body weight
Activity Intensity Weight Protein Intake
lbs grams per day

References:

  1. Cotugna, N., Vickery, C., & McBee, S. (2005). Sports nutrition for young athletes. The Journal of School Nursing, 21(6), 323-328.
  2. Bonci, L. (2010). Sports nutrition for young athletes. Pediatric Annals, 39(5), 300-309.
  3. Petrie, H., Stover, E., & Horswill, C. (2004). Nutritional concerns for the child and adolescent competitor. Nutrition, 20, 620-631.
  4. Ray, T., & Fowler, R. (2004). Current issues in sports nutrition in athletes. Southern Medical Journal, 97(9), 863-866.
  5. Campbell, W., & Geik, R. (2004). Nutritional considerations for the older athlete. Nutrition, 20, 603-608.
  6. Manore, M., Barr, S., & Butterfield, G. (2000). Nutrition and athletic performance. Medicine and Science in Sports and Exercise, 32(12), 2130-2145.
  7. Barr, S., & Rideout, C. (2004). Nutritional considerations for vegetarian athletes. Nutrition, 20, 696-703.
  8. Phillips, S. (2004). Protien requirements and supplementation in strength sports. Nutrition, 20, 689-695.