Hot off the press from three prominent nutrition and exercise associations—the American Dietetic Association, American College of Sports Medicine, and Dietitians of Canada—is the 2009 Joint Position Stand on Nutrition for Athletic Performance.
While there is little earth-shattering news in this comprehensive document (available on www.eatright.org), the authors comprehensively reviewed the research to determine which sports nutrition practices effectively enhance performance. Here are a few key points on what and when to eat to perform at your best.
1. Don't weigh yourself daily.
What you weigh and how much body fat you have should not be the sole criterion for judging how well you are able to perform in sports. That is, don't think that if you get to XX percent body fat, you will run faster. For one, all techniques to measure body fat have inherent errors. (Even BodPod can underestimate percent fat by two to three percent.) Two, optimal body fat levels depend on genetics and what is optimal for your unique body. Pay more attention to how you feel and perform than to a number on the scale.
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2. Assess your protein needs.
Protein recommendations for both endurance and strength-trained athletes range from 0.5 to 0.8 grams per pound (1.2-1.7 g/kg) body weight. For a 150-lb. athlete, this comes to about 75 to 120 g protein per day, an amount most athletes easily consume through their standard diet without the use of protein supplements or amino acid supplements. Vegetarian athletes should target ten percent more, because some plant proteins (not soy but legumes) are less well digested than animal proteins.
If you are just starting a weight-lifting program, you’ll want to target the higher protein amount. Once you have built-up your muscles, the lower end of the range is fine.
More: How Much Protein Do You Need During a Workout?
3. Assess your carbohydrate needs.
Athletes in power sports need to pay attention to carbohydrates, and not just protein. That's because strength training depletes muscle glycogen stores. You can deplete about 25 percent to 35 percent of total muscle glycogen stores during a single 30-second bout of resistance exercise.
More: Are You Eating Enough Carbs?
4. Meet your calorie needs.
Athletes who eat enough calories to support their athletic performance are unlikely to need vitamin supplements. But athletes who severely limit their food intake to lose weight (such as wrestlers, lightweight rowers, gymnasts), eliminate a food group (such as dairy, if they are lactose intolerant), or train indoors and get very little sunlight (skaters, gymnasts, swimmers) may require supplements.
5. Watch your iron.
If you are vegetarian, a blood donor, and or a woman with heavy menstrual periods, you should pay special attention to your iron intake. If you consume too little iron, you can easily become deficient and be unable to exercise energetically due to anemia. Because reversing iron deficiency can take three to six months, your best bet is to prevent anemia by regularly eating iron-rich foods (lean beef, chicken thighs, enriched breakfast cereals such as Wheaties and Total) and including in each meal a source of vitamin C (fruits, vegetables).
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6. Eating before hard exercise, as opposed to exercising in a fasted state, has been shown to improve performance. If you choose to not eat before a hard workout, at least consume a sports drink (or some source of energy) during exercise.