Working with young athletes: views of a nutritionist on the sports medicine team

DXA-derived estimates of energy balance and its relationship with changes in body composition across a season in team sport athletes

This study examined the relationship between dual-energy x-ray absorptiometry (DXA)-derived estimates of energy balance (EB) and changes in body composition across various seasonal phases in team sport athletes. Forty-five Australian rules footballers underwent six DXA scans across a 12-month period (off-season [OS, Week 0-13], early [PS1, Week 13-22] and late pre-season [PS2, Week 22-31] and early [IS1, Week 3-42] and late in-season [IS2, Week 42-51]). EB (kcal·day^-1) was estimated from changes in fat free soft tissue mass (FFSTM) and fat mass (FM) between scans according to a validated formula. An EB threshold of ± 123 kcal·day^-1 for >60 days demonstrated a very likely (>95% probability) change in FFSTM (>1.0 kg) and FM (>0.7 kg). There were small to almost perfect relationships between EB and changes in FM (r = 0.97, 95% CI, 0.96-0.98), FFSTM (r = -0.41, -0.92 to -0.52) and body mass (r = 0.27, 0.14-0.40). EB was lowest during PS1 compared to all other phases (range, -265 to -142 kcal·day^-1), with no other changes at any time. Increases in FFSTM were higher during OS compared to PS2 (1.6 ± 0.4 kg), and higher during PS1 compared to PS2, IS1, and IS2 (range, 1.6-2.1 kg). There were no changes during in-season (-0.1-0.05 kg). FM decreased only in PS1 compared to all other seasonal phases (-1.8 to -1.0 kg). Assessments of body composition can be used as a tool to estimate EB, which practically can be used to indicate athlete's training and nutrition behaviours/practices.

Adolescents involved in weight-related and power team sports have better eating patterns and nutrient intakes than non-sport-involved adolescents

OBJECTIVE

To examine eating habits and energy and nutrient intake among adolescents participating in weight-related and power team sports and non-sport-involved adolescents.

DESIGN

Data were drawn from Project EAT (Eating Among Teens), which was conducted with 4,746 adolescents from 31 middle and high schools in the Minneapolis/St Paul metropolitan area.

SETTING

Urban secondary schools.

SUBJECTS

Adolescents reporting participation in a weight-related sport, a power team sport, or no consistent participation in a sport.

MAIN OUTCOME MEASURES

Meal and snack frequency, mean energy and nutrient intake, and mean physical activity.

STATISTICAL ANALYSES PERFORMED

Analyses were conducted by sex across the three groups. General linear models were used to compare mean energy and nutrient intake, composite nutrient adequacy, and mean physical activity across the three groups. Percentages of youth meeting nutrient recommendations were compared across the three groups using chi(2) tests.

RESULTS

For both males and females, youth involved in weight-related sports ate breakfast more frequently than non-sport-involved peers (females: 3.6 and 3.2 times per week, respectively, P<0.01; males: 4.7 and 3.7 times per week, respectively, P<0.01). Weight-related and power team sport-involved youth also had higher mean protein, calcium, iron, and zinc intakes than non-sport-involved peers. However, adolescent females had low calcium intake, regardless of sports involvement (weight-related sports 1,091 mg/day, power team sports 1,070 mg/day, and non-sport-involved 1,028 mg/day, P<0.05).

CONCLUSIONS

Sport-involved adolescents have better eating habits and nutrient intake than their non-sport-involved peers. However, they are still in need of nutrition interventions, particularly around calcium intake.

Methodology of dietary assessment in athletes: concepts and pitfalls

PURPOSE OF REVIEW

Evaluation of an athlete's diet is important in both clinical practice and research. The main purpose of this review is to provide health professionals with guidance regarding the special issues that are likely to be encountered when assessing the dietary intake of sportspersons.

RECENT FINDINGS

A number of methods may be used for the dietary assessment of individuals and/or groups of athletes, including retrospective (diet recall, food-frequency questionnaire, and diet history) and prospective (diet record, duplicate portion) techniques. A 3-4-day estimated diet record is the most widely used approach, but collection of single or multiple diet recalls is also common. Care must be taken, however, to ensure that days of diet monitoring accurately reflect usual food consumption during the period of interest. Under-reporting of habitual energy intake is widespread among athletes, and its magnitude should be carefully addressed when interpreting the results of dietary assessment. Other issues, specifically related to sportspersons, that are often neglected include adequacy of standard portion sizes, frequency of snacking, fluid intake, supplement use, weight-control practices, and seasonality of sport activities and food consumption.

SUMMARY

There are subtle methodological differences in the dietary assessment of athletes and non-athletes, which, when taken into consideration, may substantially increase the quality of intake data and optimise the outcome of dietary intervention.

Joint Position Statement: nutrition and athletic performance. American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada

It is the position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of food and fluids, timing of intake, and supplement choices for optimal health and exercise performance. This position paper reviews the current scientific data related to the energy needs of athletes, assessment of body composition, strategies for weight change, the nutrient and fluid needs of athletes, special nutrient needs during training, the use of supplements and nutritional ergogenic aids, and the nutrition recommendations for vegetarian athletes. During times of high physical activity, energy and macronutrient needs-especially carbohydrate and protein intake-must be met in order to maintain body weight, replenish glycogen stores, and provide adequate protein for building and repair of tissue. Fat intake should be adequate to provide the essential fatty acids and fat-soluble vitamins, as well as to help provide adequate energy for weight maintenance. Overall, diets should provide moderate amounts of energy from fat (20% to 25% of energy); however, there appears to be no health or performance benefit to consuming a diet containing less than 15% of energy from fat. Body weight and composition can affect exercise performance, but should not be used as the sole criterion for sports performance; daily weigh-ins are discouraged. Consuming adequate food and fluid before, during, and after exercise can help maintain blood glucose during exercise, maximize exercise performance, and improve recovery time. Athletes should be well-hydrated before beginning to exercise; athletes should also drink enough fluid during and after exercise to balance fluid losses. Consumption of sport drinks containing carbohydrates and electrolytes during exercise will provide fuel for the muscles, help maintain blood glucose and the thirst mechanism, and decrease the risk of dehydration or hyponatremia. Athletes will not need vitamin and mineral supplements if adequate energy to maintain body weight is consumed from a variety of foods. However, supplements may be required by athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume high-carbohydrate diets with low micronutrient density. Nutritional ergogenic aids should be used with caution, and only after careful evaluation of the product for safety, efficacy, potency, and whether or not it is a banned or illegal substance. Nutrition advice, by a qualified nutrition expert, should only be provided after carefully reviewing the athlete's health, diet, supplement and drug use, and energy requirements.

Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance

It is the position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of food and fluids, timing of intake, and supplement choices for optimal health and exercise performance. This position paper reviews the current scientific data related to the energy needs of athletes, assessment of body composition, strategies for weight change, the nutrient and fluid needs of athletes, special nutrient needs during training, the use of supplements and nutritional ergogenic aids, and the nutrition recommendations for vegetarian athletes. During times of high physical activity, energy and macronutrient needs--especially carbohydrate and protein intake--must be met in order to maintain body weight, replenish glycogen stores, and provide adequate protein for building and repair of tissue. Fat intake should be adequate to provide the essential fatty acids and fat-soluble vitamins, as well as to help provide adequate energy for weight maintenance. Overall, diets should provide moderate amounts of energy from fat (20% to 25% of energy); however, there appears to be no health or performance benefit to consuming a diet containing less than 15% of energy from fat. Body weight and composition can affect exercise performance, but should not be used as the sole criterion for sports performance; daily weigh-ins are discouraged. Consuming adequate food and fluid before, during, and after exercise can help maintain blood glucose during exercise, maximize exercise performance, and improve recovery time. Athletes should be well-hydrated before beginning to exercise; athletes should also drink enough fluid during and after exercise to balance fluid losses. Consumption of sport drinks containing carbohydrates and electrolytes during exercise will provide fuel for the muscles, help maintain blood glucose and the thirst mechanism, and decrease the risk of dehydration or hyponatremia. Athletes will not need vitamin and mineral supplements if adequate energy to maintain body weight is consumed from a variety of foods. However, supplements may be required by athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume high-carbohydrate diets with low micronutrient density. Nutritional ergogenic aids should be used with caution, and only after careful evaluation of the product for safety, efficacy, potency, and whether or not it is a banned or illegal substance. Nutrition advice, by a qualified nutrition expert, should only be provided after carefully reviewing the athlete's health, diet, supplement and drug use, and energy requirements.

Relationship between energy deficits and body composition in elite female gymnasts and runners

PURPOSE

The purpose of this study was to evaluate energy balance and body composition in 42 gymnasts (mean age = 15.5 yr) and 20 runners (mean age = 26.6 yr), all of whom were on national teams or were nationally ranked.

METHODS

Athletes were assessed for body composition using DEXA and skinfolds, and energy balance was determined with a Computerized Time-Line Energy Analysis (CTLEA) procedure.

RESULTS

Results from the CTLEA were assessed as the number of within-day energy deficits (largest and frequency) and within-day energy surpluses (largest and frequency). There was a significant difference (P = 0.000) in the mean number of hourly energy deficits > 300 kcal experienced by gymnasts (9.45 +/- 6.00) and runners (3.70 +/- 5.34). There was also a significant difference (P = 0.001) in the mean number of hourly energy surpluses > 300 kcal experienced by gymnasts (1.40 +/- 3.04) and runners (6.20 +/- 5.50). The mean largest daily energy deficit was 743 (+/- 392) kcal for gymnasts and 435 (+/- 340) kcal for runners. The mean largest daily energy surplus was 239 (+/- 219) kcal for gymnasts, and 536 (+/- 340) kcal for runners. There was a significant relationship between the number of daily energy deficits > 300 kcal and DEXA-derived body fat percent for gymnasts (r = 0.508; P = 0.001) and for runners (r = 0.461; P = 0.041). There was also a negative relationship between the largest daily energy surplus and DEXA-derived body fat percentage for gymnasts (r = -0.418; P = 0.003). Using the energy balance variables, age, and athlete type (artistic gymnast, rhythmic gymnast, middle-distance runner, long-distance runner) as independent variables in a forward stepwise regression analysis, a small but significant amount of variance was explained in DEXA-derived (P = 0.000; R2 = 0.309) and skinfold-derived (P = 0.000; R2 = 0.298) body fat percent by the number of energy deficits > 300 kcal and age.

CONCLUSIONS

These data suggest that within-day energy deficits (measured by frequency and/or magnitude of deficit) are associated with higher body fat percentage in both anaerobic and aerobic elite athletes, possibly from an adaptive reduction in the REE. These data should discourage athletes from following restrained or delayed eating patterns to achieve a desired body composition.

Chronic dieting in active women: what are the health consequences?

Evidence suggests that there is ever increasing pressure on American women to be thin. This pressure drives women to want to be thinner than what might be realistically achieved or required for good health. Our goal as nutrition and health professionals is to help women achieve and maintain a healthy body weight throughout the life-cycle. This includes helping young females accept their body size and shape as well and placing more emphasis on health and fitness than on weight in this population. This process begins with the identification of what constitutes a healthy body weight for a particular individual based on genetic, physiological, social, and psychological factors. In addition, it should be a weight that can be realistically maintained while keeping risk factors for chronic disease low. Table 1 outlines some strategies for helping individuals to identify and maintain a healthy body weight.