Effects of habitual physical activity on the resting metabolic rates and body compositions of women aged 35 to 50 years.

OBJECTIVE: To examine the effect habitual physical activity has on resting metabolic rate (RMR) and body composition (fat-free mass[FFM], fat mass, and percent body fat) in active compared to sedentary adult women. DESIGN: RMR was measured (by indirect calorimetry) twice after a 12-hour fast at the same point of the menstrual cycle and 48 hours after exercise. FFM, fat mass and percent body fat were measured using whole body air displacement plethysmography. Energy intake and expenditure were determined using 7-day weighed-food records and activity logs. SUBJECTS: Healthy, weight-stable premenopausal women aged 35 to 50 years classified as either active (approximately 9 hours per week of physical activity for 10 or more years) (n= 18) or sedentary (approximately 1 hour per week of physical activity) (n= 14). STATISTICAL ANALYSES: Analysis of covariance was used to investigate differences in mean RMR (kcal/day) between the groups adjusted for FFM, and independent t tests were used to determine differences in demographic, energy expenditure, and diet variables. RESULTS: Percent body fat and fat mass were lower (P<.0005) and RMR (adjusted for FFM) was significantly higher in the active women (P=.045) compared with sedentary controls. In the active and sedentary groups respectively, mean adjusted RMR was 1,510 kcal/day and 1,443 kcal/day, body fat was 18.9% and 28.8%, and fat mass was 11.1 kg and 18.8 kg. Groups were similar in body mass, FFM, body mass index, and age. Mean energy balance appeared to be more negative in the active group (P=.0059) due to significantly higher mean self-reported energy expenditures (P=.0001) and similar mean self-reported energy intakes (P=.52) compared with sedentary controls. These data indicate that active women who participate in habitual physical activity can maintain lower body fat and a higher RMR than sedentary controls with similar body mass, FFM, and body mass index. APPLICATIONS/CONCLUSIONS: This research supports and emphasizes the benefits of habitual physical activity in maintaining RMR and lower body fat levels in middle-aged women.

Postexercise oxygen consumption and substrate use after resistance exercise in women.

OBJECTIVE: This study investigated the acute effects of 45 min of resistance exercise (RE) on excess postexercise oxygen consumption (EPOC) and substrate oxidation 120 min after exercise in moderately trained women. METHODS: Ten RE trained women (age = 29 +/- 3 yr; ht = 168 +/- 8.3 cm; wt = 59 +/- 5.7 kg; VO2max = 38.3 +/- 4.7 mL.kg-1.min-1) underwent two trials: control sitting and RE. Subjects acted as their own controls in a random counterbalanced design. A 2-d nonexercise period was established between testing trials. Oxygen consumption (VO2) and respiratory exchange ratio (RER) were measured continuously by indirect calorimetry before, during, and after exercise and on a separate control day. RE consisted of 3 sets of 10 exercises at 10-repetition maximum with a 1-min rest period between each set. Fingertip samples of blood lactate concentration [BL] were collected immediately postexercise and every 30 min thereafter until [BL] returned to resting baseline values after exercise. RESULTS: The overall 2-h EPOC was 6.2-L (RE = 33.4 +/- 5.1 L vs control = 27.2 +/- 0.3 L), corresponding to an 18.6% elevation over the control period. RER was significantly (P < 0.01) below the control RER from minute 30 to minute 120 postexercise (RE = 0.75 +/- 0.01 vs control = 0.85 +/- 0.01). During the last 30 min of recovery, VO2 and [BL] had returned to control/baseline values and fat oxidation was significantly (P < 0.0001) higher (29.2 vs 16.3 kcal) after RE compared with the control trial. CONCLUSION: These data indicate that in young RE trained women, acute RE produces a modest increase in VO2 during a 2-h recovery period and an increase in fat oxidation.

Effect of physical activity on thiamine, riboflavin, and vitamin B-6 requirements.

Because exercise stresses metabolic pathways that depend on thiamine, riboflavin, and vitamin B-6, the requirements for these vitamins may be increased in athletes and active individuals. Theoretically, exercise could increase the need for these micronutrients in several ways: through decreased absorption of the nutrients; by increased turnover, metabolism, or loss of the nutrients; through biochemical adaptation as a result of training that increases nutrient needs; by an increase in mitochondrial enzymes that require the nutrients; or through an increased need for the nutrients for tissue maintenance and repair. Biochemical evidence of deficiencies in some of these vitamins in active individuals has been reported, but studies examining these issues are limited and equivocal. On the basis of metabolic studies, the riboflavin status of young and older women who exercise moderately (2.5-5 h/wk) appears to be poorer in periods of exercise, dieting, and dieting plus exercise than during control periods. Exercise also increases the loss of vitamin B-6 as 4-pyridoxic acid. These losses are small and concomitant decreases in blood vitamin B-6 measures have not been documented. There are no metabolic studies that have compared thiamine status in active and sedentary persons. Exercise appears to decrease nutrient status even further in active individuals with preexisting marginal vitamin intakes or marginal body stores. Thus, active individuals who restrict their energy intake or make poor dietary choices are at greatest risk for poor thiamine, riboflavin, and vitamin B-6 status.

Behavioral, psychological, and physical characteristics of female athletes with subclinical eating disorders.

The purpose of this study was to delineate and further define the behavioral, psychological, and physical characteristics of female athletes with subclinical eating disorders. Subjects consisted of 24 athletes with subclinical eating disorders (SCED) and 24 control athletes. Group classification was determined by scores on the Eating Disorder Inventory (EDI), the Body Shape Questionnaire (BSQ), and a symptom checklist for eating disorders (EDI-SC). Characteristics representative of the female athletes with subclinical eating disorders were derived from an extensive health and dieting history questionnaire and an in-depth interview (the Eating Disorder Examination). Energy intake and expenditure (kcal/d) were estimated using 7-day weighed food records and activity logs. The characteristics most common in the female athletes with subclinical eating disorders included: (a) preoccupation with food, energy intake, and body weight; (b) distorted body image and body weight dissatisfaction; (c) undue influence of body weight on self-evaluation; (d) intense fear of gaining weight even though at or slightly below ( approximately 5%) normal weight; (e) attempts to lose weight using one or more pathogenic weight control methods; (g) food intake governed by self-hatred upon breaking a rule; (h) absence of medical disorder to explain energy restriction, weight loss, or maintenance of low body weight; and (i) menstrual dysfunction. Awareness of these characteristics may aid in more timely identification and treatment of female athletes with disordered eating patterns and, perhaps, prevent the development of more serious, clinical eating disorders.

Nutritional needs of the female athlete.

US women, including female athletes, are under ever increasing pressure to be thin ar thinner. this pressure to achieve and maintain a low body weight leads to potentially harmful patterns of long-term dieting or disordered eating, which can affect long-term health. Some of the health consequences of long-term energy restriction in female athletes may include poor energy and nutrient intakes, poor nutritional status, decreased RMR and total daily energy expenditure, increased psychological stress and risk for a clinical eating disorder, and increased risk for exercise-induced amenorrhea and osteoporosis. Female athletes participating in thin-build sports may be at risk for the disorders of the female athlete triad: disordered eating, amenorrhea, and osteoporosis. This triad of disorders can also produce severe health consequences that can influence present and future health. Strategies for helping active women get off the dieting "bandwagon" requires the identification of an appropriate and healthy body weight, good eating and exercise habits, and techniques for maintaining these habits throughout life.

Energy and nutrient status of amenorrheic athletes participating in a diet and exercise training intervention program.

Chronic energy deficit is one of the strongest factors contributors to exercise-induced menstrual dysfunction. In such cases, macro- and micronutrient intakes may also be low. This study presents the results of a diet and exercise training intervention program. designed to reverse athletic amenorrhea, on improving energy balance and nutritional status in 4 amenorrheic athletes. The 20-week program provided a daily sport nutrition supplement and 1 day of rest/week. The program increased protein intakes for the 3 athletes with a protein deficit to within the recommended levels for active individuals. Micronutrient intakes increased, as did serum concentrations of vitamin B12, folate, zinc, iron, and ferritin. These results indicate that some amenorrheic athletes have poor nutritional status due to restricted EIs and poor food selections. A sport nutrition supplement may improve energy balance and nutritional status in active amenorrheic women.

Lower daily energy expenditure as measured by a respiratory chamber in subjects with spinal cord injury compared with control subjects.

BACKGROUND: This study was designed to determine the effect of chronic spinal cord injury on daily energy expenditure. OBJECTIVE: We hypothesized that both resting and total energy expenditure would be lower in spinal cord-injured (SCI) subjects than in control subjects because of lower sympathetic nervous system activity and reduced levels of physical activity in SCI subjects. DESIGN: Twenty-four-hour energy expenditure (24-h EE), resting metabolic rate (RMR), sleeping metabolic rate, spontaneous physical activity, the thermic effect of food (TEF), and 24-h respiratory quotient were measured by using a respiratory chamber in 10 male SCI subjects (injury ranged from level C6 to L3) and 59 age-matched, noninjured, male control subjects. RESULTS: The 24-h EE was lower in SCI than in control subjects (7824 +/- 305 compared with 9941 +/- 188 kJ, P < 0.01). After adjustment for fat-free mass, fat mass, and age, 24-h EE was still lower (-753 kJ/d, P < 0.01) in SCI than in control subjects. Spontaneous physical activity measured by a radar system was also significantly lower (4.6 +/- 0.6% compared with 6.5 +/- 0.3% of time, P < 0.01) in SCI than in control subjects. In absolute value (7347 +/- 268 compared with 9251 +/- 1326 kJ/d, P < 0.01) or after adjustment for fat-free mass, fat mass, and age (-678 kJ/d, P < 0.01), RMR was also lower in SCI than in control subjects. TEF was significantly lower in SCI than in control subjects (987 +/- 142 compared with 1544 +/- 213 kJ/d, representing 12.9% and 15.9% of total energy intake, respectively, P < 0.05). The sleeping metabolic rate and 24-h respiratory quotient did not differ significantly between groups. CONCLUSIONS: The 24-h EE was significantly lower in SCI than in control subjects. This difference can be explained by the lower levels of physical activity, and lower RMR and TEF values, in SCI subjects.

Social physique anxiety in postmenopausal women.

Social physique anxiety (SPA), the degree to which individuals become anxious when others observe their bodies, is an important concept for postmenopausal women because it may be directly related to their physical activity behavior. Women with high levels of social physique anxiety may not participate in health-enhancing physical activity. Therefore, the main purpose of this study was to examine SPA in postmenopausal women relative to leisure time physical activity (LTPA, activities such as exercise, recreation, and sports). Other factors, such as percent body fat, body fat distribution, age, and hormone replacement therapy status were also examined for their relationship to SPA. Women who expended < or = 500 kcal.wk-1 in LTPA had significantly higher SPA than women who expended > or = 2,000 kcal.wk-1, independent of percent body fat. Women with more than 37.5% body fat had significantly higher SPA than those with less than 37.5% body fat. Women with upper BFD (waist-to-hip ratio or WHR > 0.85) had higher SPA than women with lower BFD (WHR < 0.75). There were no differences in SPA relative to age or HRT status. It appears that a sedentary lifestyle, high percent body fat, and upper body fat distribution are associated with increased SPA in postmenopausal women, thus health promotion professionals should be aware of these concerns when developing physical activity interventions for postmenopausal women.

Nutritional status of female athletes with subclinical eating disorders.

OBJECTIVE: To assess the energy and nutritional status of female athletes with subclinical eating disorders and compare them with that of control subjects and standard norms. DESIGN: Group classification (subclinical eating disorder or control) was based on responses to a health and diet history questionnaire, a battery of self-report eating disorder questionnaires, and an in-depth interview. Energy and nutrient intakes and energy expenditure were determined by means of 7-day weighed food records and 7-day activity logs. Micronutrient status was assessed for iron, zinc, magnesium, vitamin B-12, and folate. SUBJECTS: Twenty-four female athletes with subclinical eating disorders and 24 female control athletes. STATISTICAL ANALYSES: Descriptive statistics were used to analyze demographic data. One-way analysis of variance was used to determine group differences in energy and nutrient intakes, energy balance, and blood values. RESULTS: Groups were similar in age, height, weight, fat-free mass, and body mass index. Mean energy intake was lower in the group with subclinical eating disorders (1,989 kcal/day) than in the control group (2,300 kcal/day; P=.004), whereas mean energy expenditures were similar (2,405 and 2,293 kcal/day, respectively). The group with subclinical eating disorders had significantly (P<.05) lower mean protein and fat intakes compared with the control group; mean micronutrient intakes were not significantly different. Mean status measures for iron, zinc, magnesium, vitamin B-12, and folate were within the normal ranges for both groups and no differences were noted between the groups. A similar number of athletes within each group used vitamin/mineral supplements < or = 4 times per week. CONCLUSION: Although female athletes with subclinical eating disorders had dietary intakes of energy, protein, carbohydrate, and certain micronutrients that were below recommended levels, micronutrient status appeared relatively unaffected, probably due to their use of supplements.

Adiposity, plasma leptin concentration and reproductive function in active and sedentary females.

OBJECTIVE: Circulating leptin has recently been proposed as the peripheral signal indicating the adequacy of nutritional status for reproductive function. To test whether low plasma leptin concentration for a given degree of adiposity is associated with menstrual dysfunction, we measured plasma leptin concentration and body composition in young premenopausal women with normal or abnormal reproductive function. DESIGN: Fasting plasma leptin concentration (ELISA), body composition (dual energy X-ray absorptiometry) and menstrual status (menstrual history and hormonal profile) were assessed in 34 premenopausal women characterized by different levels of physical activity. RESULTS: Body fat content and plasma leptin concentration were both reduced in women with impaired reproductive function (amenorrheic < anovulatory < eumenorrheic women). However, after adjusting plasma leptin concentration for percentage body fat, there was no independent association between leptin and menstrual function. CONCLUSION: Menstrual abnormalities in young premenopausal women seem to occur as a consequence of the linear decline in adiposity and plasma leptin concentration observed in response to inadequate nutritional status. Levels of adiposity below 15% and plasma leptin concentration below 3 ng/ml are more likely to be associated with impaired reproductive function.

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.

Role of energy balance in athletic menstrual dysfunction.

The cessation of menstrual function in the female athlete may reflect her inability to adapt to the environmental and lifestyle stressors associated with training and competition. As society's emphasis on thinness, dieting, and exercise continues to increase, so will the incidence of menstrual dysfunction in active females. Unfortunately, some individuals view athletic menstrual dysfunction as a benign consequence of strenuous exercise. Conversely, it is most likely a strong indicator of overtraining and a marker for future decrements in performance, and it can have long-term health consequences. Thus, it is imperative that the active female be appropriately educated regarding the adverse consequences of menstrual dysfunction and the interventions available. This paper focuses on the most current information regarding athletic menstrual dysfunction and its multifactorial etiology, especially the role of energy drain. In addition, common misconceptions, adverse health and performance effects, and available treatment options are discussed.

Treatment of athletic amenorrhea with a diet and training intervention program.

The purpose of this study was to determine the effect of a 15-week diet and exercise intervention program on energy balance, hormonal profiles, body composition, and menstrual function of an amenorrheic endurance athlete. The intervention program reduced training 1 day/week and included the use of a sport nutrition beverage providing 360 kcal/day. Three eumenorrheic athletes served as a comparison group and were monitored over the same 15-week period. The amenorrheic athlete experienced a transition from negative to positive energy balance, increased body fat from 8.2 to 14.4%, increased fasting luteinizing hormone (LH) from 3.9 to 7.3 mIU/ml, and decreased fasting cortisol from 41.2 to 33.2 micrograms/dl. The eumenorrheic subjects showed a 0.4% reduction in body fat, a decrease in follicular phase levels of LH from 7.9 to 6.5 mIU/ml, and no change in cortisol. These results suggest that nonpharmacological treatment can contribute to reestablishing normal hormonal profiles and menstrual cyclicity in amenorrheic athletes.

Effects of diet and diet-plus-exercise programs on resting metabolic rate: a meta-analysis.

Studies examining the effects of diet (D) and diet-plus-exercise (DE) programs on resting metabolic rate (RMR) report equivocal results. The purpose of this study was to use meta-analysis to determine if exercise prevents the decrease in RMR observed with dieting. Results from the 22 studies included in this analysis revealed that the majority of studies used female subjects ages 31-45 years, who were fed a relatively low-fat, high-carbohydrate diet of less than 5,023 kJ.day-1. The predominant prescribed exercise was aerobic in nature, 31-60 min in duration, performed 4-5 days per week, and of moderate intensity (51-70% of VO2max). Contrary to what is reported in narrative reviews, RMR decreased significantly with both D and DE programs, and the drop with D was significantly greater than that with DE. In conclusion, the addition of exercise to dietary restriction appears to prevent some of the decrease in RMR observed in premenopausal women.

Predicted and measured resting metabolic rate of male and female endurance athletes.

OBJECTIVE: To measure the resting metabolic rate (RMR) of a group of endurance-trained male and female athletes and to compare it with values predicted using published equations. DESIGN: RMR was measured twice: 1 week apart for the men and approximately 1 month apart for the women. RMR was predicted using equations of Harris and Benedict, Owen et al, Mifflin et al, and Cunningham. SUBJECTS/SETTING: Subjects were 37 trained endurance athletes (24 men, 13 women) who had participated in studies previously completed in our laboratory. MAIN OUTCOME MEASURES: The primary outcome measure was the comparison of predicted RMR with measured RMR. An exploratory procedure for the determination of predictive variables in these athletes was also performed. STATISTICAL ANALYSES PERFORMED: The Root Mean Squared Prediction Error method was used to compare predicted RMR with measured RMR. The maximum R2 procedure method was used to determine the best possible combination of four variables that explained the largest amount of variance in RMR. RESULTS: The Cunningham equation was found to predict measured RMR most accurately (within 158 kcal/d for men and 103 kcal/d for women). Fat-free mass was the best predictor of RMR in men, whereas energy intake was the best predictor in women. APPLICATIONS/CONCLUSIONS: The Cunningham equation provides an accurate estimate of RMR when determining energy needs of highly active people. Equations specific to athletes need to be developed. Factors in addition to body weight, height, and age should be investigated as possible predictor variables in athletes.

Blood pressure responses of white men with hypertension to two low-sodium metabolic diets with different levels of dietary calcium.

OBJECTIVE: To compare the blood pressure responses of men with hypertension consuming low-sodium (Na) metabolic diets differing in dietary calcium (Ca) for two 6-week periods. SUBJECTS: White men who had hypertension, were nonsmokers, and were sedentary. INTERVENTION: This study consisted of two separate 6-week metabolic feeding periods. In the first period, a high-Ca group (n = 6) was fed 1,400 mg Ca per day. In the second period, a low-Ca group (n = 5) was fed 400 mg Ca per day. Both groups were fed 1,500 mg Na per day. MAIN OUTCOME MEASURES: Blood pressure; urine and blood measured for electrolyte, calcitriol, renin, and parathyroid hormone (PTH) levels. To measure typical nutrient intakes, 3-day dietary records were collected before the beginning of each treatment period. STATISTICAL ANALYSES PERFORMED: Repeated-measures analysis of variance and split-plot analysis of variance were used to analyze, respectively, blood pressure responses and response variables over time. RESULTS: In both groups, serum Na level decreased (P < .05) over the 6-week period; urine Na decreased (P < .05) only in the low-Ca group. Serum PTH level decreased (P < .05) in the high-Ca group and increased (P < .05) in the low-Ca group; no change occurred in serum calcitriol level. Diastolic blood pressure decreased (8 mm Hg) in the low-Ca group (P < .05). The low-Ca group showed an 8% to 9% decrease in both systolic and diastolic blood pressure vs a 2% to 3% decrease in the high-Ca group. We also examined how the metabolic diet differed from subjects' typical diet. Results showed a positive correlation between the change in Na intake (usual to metabolic diet) and the change in systolic and diastolic blood pressure in both groups (P < .04). Results also showed a negative correlation between the change in the ratio of Na to Ca (usual to metabolic diet) and the change in diastolic blood pressure in the low-Ca group (P < .03). Directional change in blood pressure (either increase or decrease) could be predicted on the basis of how much the Na and Ca in the metabolic diet differed from subject's typical diet. APPLICATIONS: Results of this study suggest that in the dietary management of hypertension it may be more important to focus on specific changes in a person's diet (eg, decreasing Na intake by 1,000 mg/day and increasing Ca intake by 400 mg/day) rather than setting specific levels of Na and Ca to be consumed.

Daily energy expenditure in male endurance athletes with differing energy intakes.

The 24-h energy expenditure (24-h EE), resting EE (REE), sleeping EE (SEE), and spontaneous physical activity (SPA) were compared between six male endurance athletes whose reported energy intake was low (LOW) and did not match that theoretically required for weight maintenance and four whose reported energy intake appeared adequate (ADQ) and matched their estimated EE. Groups did not differ in age, body weight, fat-free mass, and daily EE estimated from activity records. The LOW athletes reported an energy intake 6338 +/- 2164 kJ.d-1 less than estimated EE. The 24-h EE, REE, SEE, and SPA of the LOW athletes were significantly lower than the ADQ athletes (862, 523, 770 kJ.d-1, and 43 min.d-1, respectively). Using all subjects, there was a significant positive correlation between REE and free thyroxine (FT4) (r = 0.82) and SEE and FT4 (r = 0.66). Thus, part of the LOW athlete's ability to maintain body weight on a seemingly low energy intake appears due to a lower daily sedentary EE.

The prevalence and consequences of subclinical eating disorders in female athletes.

A growing body of evidence suggests that the prevalence of eating disorders and excessive concerns regarding body weight in certain subpopulations of female athletes are increasing. The pressure on female athletes to improve their performances and physiques, coupled with the general sociocultural demand placed on all women to be thin, often results in attempts to achieve unrealistic body size and body weight goals. For some female athletes the pressure to achieve and maintain a low body weight leads to potentially harmful patterns of restrictive eating or chronic dieting. This paper seeks to further delineate the characteristics of a recently identified subclinical eating disorder in female athletes: anorexia athletica. Research studies that support the existence of subclinical eating disorders will be reviewed. In addition, the possible physiological and psychological consequences of subclinical eating disorders will be explored.

Vitamin B6 and exercise.

This paper presents an overview of vitamin B6 and exercise, including the role that vitamin B6 plays in gluconeogenesis and glycogenolysis and changes in vitamin B6 metabolism during exercise. The dietary vitamin B6 intakes of athletes are also reviewed. Most studies report that male athletes have adequate dietary intakes of vitamin B6, whereas some females, especially those with low energy intakes, appear to have low vitamin B6 intakes. Few studies have assessed the vitamin B6 status of nonsupplementing athletes using the recommended status criteria. The role that vitamin B6 may play in attenuating the rise in plasma growth hormone observed during exercise is also reviewed. Finally, recommendations are given for further research in the area of vitamin B6 and exercise.