DEUTZ, R. C., D. BENARDOT, D. E. MARTIN, and M. M. CODY. Relationship between energy deficits and body composition in elite female gymnasts and runners. Med. Sci. Sports Exerc., Vol. 32, No. 3, pp. 659–668, 2000.
Purpose: The purpose of this study was to evaluate energy balance and body composition in 42 gymnasts (-× age = 15.5 yr) and 20 runners (-× 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 -× 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 -× number of hourly energy surpluses > 300 kcal experienced by gymnasts (1.40 ± 3.04) and runners (6.20 ± 5.50). The -× largest daily energy deficit was 743 (± 392) kcal for gymnasts and 435 (± 340) kcal for runners. The -× 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.
Energy balance is an important factor in performance (47), body fat percentage (17,34), menstrual status (12,30,31,44), growth (24,45), and injury rates (13,35,36) among elite athletes. Nevertheless, this is an area of nutrition that is not commonly given the attention it deserves by coaches, health professionals, and the athletes themselves. Athletes who participate in sports in which appearance is an important factor in success (i.e., figure skating, rhythmic and artistic gymnastics, diving, etc.) often purposefully initiate a restrained eating regimen to achieve a desired body fat level or body weight, thereby negatively impacting energy balance (23,24,44). Athletes and coaches commonly believe that a reduction in weight or body fat will improve sports performance, even when weight and body fat are well within the norms for elite level athletes (1,44). However, there is an increasing body of evidence that the energy imbalance created by restrained or poorly timed eating patterns may be associated with lower resting energy expenditure (34,46), higher body fat (4), higher injury rates (30,36), menstrual dysfunction (44), and lower bone density (2,41).
Studies of nonathletes and athletes have demonstrated that the human adaptive response to energy restriction is a reduction in the resting metabolic rate (RMR), with a possible associated increase in fat storage (17,28,34). It is unclear, however, whether regular intensive exercise training blunts or exacerbates the reduction in RMR and the associated increase in body fat storage that is caused by energy restriction (8,22,25,26).
In most studies evaluating the energy balance of athletes, energy intake has been estimated via multiple-day food records, with energy expenditure being estimated by totaling RMR, general daily activity, specific sport activity, and the thermic effect of food. Some recent studies have evaluated the energy expense of sport activity via double-labeled water (H2O18) (7,37,38,43). Regardless of the measurement technique used, athletes who are identified as either energy deficient or energy replete have different resting energy expenditures. Whether they are runners, wrestlers, or gymnasts, those with energy deficits generally have significantly lower resting energy expenditures than those who are energy replete (16,21,27,42,46).
Energy intake and expenditure have typically been evaluated in 24-h time blocks. However, in doing so the periods of energy imbalance that occur within a day cannot be evaluated. To determine whether within-day energy imbalance is an important factor in body fat level, Benardot developed a method for simultaneously estimating energy intake and energy expenditure (4). The energy expenditure procedure for this method follows the procedure described by the National Research Council Subcommittee on the Tenth Edition of the RDA (29). When applied to a small sample of elite female gymnasts, within-day energy imbalance was found to be an important factor in predicting body fat percentage. Using this technique, the present study evaluated the relationship of 24-h energy balance and within-day energy balance with body fat percentage in four groups of elite athletes having different training dynamics: artistic and rhythmic gymnasts and middle- and long-distance runners.
Laboratory for Elite Athlete Performance, Center for Sports Medicine, Science & Technology, College of Health and Human Sciences, Georgia State University, Atlanta, GA 30303
Submitted for publication September 1998.
Accepted for publication April 1999.
Address for correspondence: Dan Benardot, Ph.D., R.D., L.D., Laboratory for Elite Athlete Performance, Box 873 Univer- sity Plaza, Georgia State University, Atlanta, GA 30303. E-mail: firstname.lastname@example.org.