November 2009 Issue
Winning Strategy — Address Weight and Energy Intake to Improve Athletes’ Performance
By Marissa R. Beck, MS
Today’s Dietitian
Vol. 11 No. 11 P. 14
A wrestler runs on the treadmill in a sweatshirt and sweatpants, determined to shed another 5 lbs before his final weigh-in. He has a few more days to starve, sweat, and purge excess calories. Thoughts of food overwhelm his senses; he has trouble concentrating in class. As soon as he makes weight, he and his wrestling buddies will binge, a typical prematch ritual.
Unhealthy eating patterns span across all sports. Young athletes may feel pressured to achieve a lean physique, even if their current body weight is appropriate for both health and performance. Certain sports that emphasize weight (eg, wrestling, lightweight rowing) or leanness (eg, dance, gymnastics, figure skating, diving) demand specific body weights and compositions that can pressure a young athlete to reduce body weight inappropriately.
Dietitians can help athletes who are practicing harmful methods of weight control. They should recognize that balancing intense workouts and food intake is not an easy task. It can intimidate and frustrate athletes and, worst of all, it can negatively affect their health if not done properly. Dietitians can be athletes’ banister of support while helping them achieve adequate energy intake, their own optimal weight, and balance with their diet.
Address Inadequate Energy Intake
Consuming adequate calories is one of the most important challenges young athletes face, as it is key to optimal performance. Low energy intake is associated with detrimental effects. At first, it will compromise muscle mass and glycogen stores. Loss of menstrual function, as well as bone and muscle mass, and an increased risk of illness, fatigue, and injury can occur when energy deficits are extreme. According to the new American Dietetic Association (ADA) and American College of Sports Medicine (ACSM) 2009 Position Stand, inadequate energy intake in relation to energy expenditure compromises performance, which in turn compromises the benefits of training. On the other hand, consuming adequate energy will safeguard body composition and immune, endocrine, and musculoskeletal function and maximize training’s positive effects.
Some athletes intentionally underfuel their bodies. A 1994 review of disordered eating in active and athletic women in the Clinical Journal of Sport Medicine found that many factors contribute to the development of harmful behaviors, such as school sports programs that push athletes to the limits of training, social factors (eg, Western cultures’ idealization of thinness), and psychological/personality factors (eg, poor coping skills, perfectionism, low self-esteem). In a study of 48 female athletes, one half of which had subclinical eating disorders, more than 70% of the athletes with eating disorders had a preoccupation with body weight.1
Coaches and dietitians can recognize eating issues early on by searching for clues in body weight trends. A telltale sign of inadequate energy intake in females is an irregular or absent menstrual cycle, which occurs due to an energy imbalance. Loss of a menstrual cycle is part of the “female athlete triad,” which is linked to inadequate intake. This condition is characterized by amenorrhea, disordered eating, and osteoporosis. In males, some signs are having a preoccupation with “bulking up” and losing a noticeable amount of weight.
Assess Body Weight
There isn’t an ideal body weight or body composition for any particular sport. The ADA/ACSM position stand states that an optimal competitive body weight should be determined when an athlete is healthy and performing at his or her best. That said, there are minimal levels of body fat that are compatible with health. For males, 5% is the lowest; for females, it’s 12%.2 While an athlete’s body fat percentage differs depending on his or her specific sport, it’s important to measure trends, not numbers. Since body composition is one of the many factors that contribute to optimal exercise performance, using specific measurement techniques may estimate an athlete’s potential for success in a sport.
Some common measurement techniques that assess body composition include dual-energy x-ray absorptiometry (DXA), which measures both bone and body composition, and the Bod Pod, which assesses body composition through air displacement plethysmography. Less expensive and easier to use methods are skin-fold measurements and bioelectrical impedance analysis, which is based on the notion that an electrical signal conducts better through lean tissue than fat or bone. Note that these techniques have margins of error of approximately 4%; therefore, it is not appropriate to set specific body fat goals but rather target ranges. For example, the ACSM norm is 22% to 25% body fat for females and 15% to 18% for males.3
Maintaining a good body composition will ensure that the athlete doesn’t use his or her muscle stores for energy. Meeting energy needs is a priority for athletes’ body composition and sustaining high levels of performance.
Estimate Energy and Macronutrient Requirements
The position stand recommends using the 2005 Dietary Guidelines and the Dietary Reference Intakes (DRIs) for active individuals (see Figure 1 below) or the Harris-Benedict equation to estimate individual needs. There are inherent dangers of restricting energy, such as those discussed previously; eliminating certain macronutrients can incur similar issues.
According to the position stand, the current guidelines for macronutrient amounts depend on the athlete’s sex, total daily energy expenditure, type of sport, and duration, frequency, and intensity of exercise. Carbohydrate intake, ranging from 6 to 10 g/kg body weight, is important to maintain blood glucose levels and replace muscle glycogen. Protein amounts for both endurance and strength-training athletes should range from 1.2 to 1.7 g/kg body weight. Although high-protein diets are popular among athletes, amino acid supplementation has not been shown to positively impact exercise performance, according to the position stand. It also states that professionals should conduct a thorough nutrition assessment before recommending protein powders and/or amino acid supplementation. Fat should range from 20% to 35% of total energy intake, with 10% from saturated, 10% from polyunsaturated, 10% from monounsaturated, and sources from essential fatty acids.
The Training Diet
Athletes should consume adequate food and fluid before, during, and after exercise to help maintain blood glucose concentration, maximize exercise performance, and improve recovery time. The position stand recommends a meal or snack before exercising that is high in carbohydrates, moderate in protein, and low in fat and fiber for quick gastric emptying (eg, a bagel with a handful of raisins or fresh fruit). Every athlete will have his or her own preferences and will measure tolerance on a trial-and-error basis.
During exercise that lasts longer than 60 minutes, athletes should consume fluids and carbohydrates to decrease their risk of dehydration and maintain blood glucose levels. Sports beverages contain carbohydrates and electrolytes, which provide fuel for muscles. The recommendation is to consume 30 to 60 g/hour of carbohydrates. Postexercise, athletes should consume enough fluid, electrolytes, energy, and carbohydrates to replace muscle glycogen and start the recovery process. Timing is essential. In the first 30 minutes, they should consume 1 to 1.5 g/kg body weight; they should consume the same amount every two hours for the next four to six hours. Along with carbohydrates, athletes should consume protein to help repair muscle tissue.
Recommendations for RDs
According to the position stand, when assessing athletes’ optimal body weight, dietitians should help them set realistic goals. Guiding athletes toward eating balanced, appropriately sized meals and snacks throughout the day will help them sustain their weight and improve exercise performance in the long term.
Body fat percentages vary according to the individual athlete and his or her sport. It is important to establish a range of values vs. specific ones. Dietitians can help athletes who participate in sports with weight classifications safely and effectively lose weight and can help coaches and athletes recognize that there is no ideal body weight for any sport or player. There is only an optimal body weight and composition for each individual athlete.
— Marissa R. Beck, MS, completed her master’s degree in applied physiology and nutrition at Teachers College, Columbia University and will become a fully credentialed registered dietitian.
References
1. Beals KA, Manore MM. Behavioral, psychological, and physical characteristics of female athletes with subclinical eating disorders. Int J Sport Nutr and Exerc Metab. 2000;10(2):128-143.
2. Heymsfield S, Lohman T, Wang Z, Going S. Human Body Composition. 2nd ed. Champaign, Ill.: Human Kinetics; 2005.
3. American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription. 6th ed. Baltimore: Lippincott Williams & Wilkins; 2000.
Figure 1: The Dietary Reference Intake (DRI) Method for Estimating Energy Requirements for Adults
The DRI method for estimating energy requirements of an adult male = For an adult female, estimated energy requirements = |
— Source: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Washington, D.C.: National Academies Press; 2005.