Comparison of the body mass index to other methods of body fat evaluation in ethnic Japanese and Caucasian adolescent girls

OBJECTIVE: The aim of this study was to assess the body mass index (BMI) and its relationship with other methods of body fat evaluation in pre- and post-menarcheal, Japanese and Caucasian female adolescents, using two different cut-off points for obesity: 28% and 30%. DESIGN: A cross-sectional study with incomplete sampling, using the subject as the evaluation unit. SUBJECTS: A total of 436 Japanese and Caucasian female adolescents in two age groups: 10-11 (pre-menarcheal adolescent); and 16-17 (post-menarcheal adolescents). METHODS: For the BMI the cut-off point for thinness was set at the 5th percentile of the BMI distribution of the NCHS reference population and the cut-off point for overweight and obesity was set at the 85th percentile. Body composition was assessed using foot-to-foot bioelectrical impedance analysis (BIA), near-infrared interactance (NIR) and Slaughter skinfold equations (SKI). The statistical comparison of the methods was performed using the kappa agreement test and the McNemar disagreement test. RESULTS: In the 10- and 11-y-old girls, the BMI was considerably and significantly correlated with the other methods. The major agreements were: in Japanese adolescents BMI x NIR=82.3% (cut-off point of 28%), BMI x BIA=85.7% (cut-off point of 30%); in Caucasian adolescents BMI x NIR=80.7% (cut-off point of 28%), BMI x BIA=87.4% (cut-off point of 30%). The disagreement above the diagonal between BMI x NIR was higher within the two groups for both the cut-off points, revealing that the girls identified as obese by the BMI were considered eutrophic by NIR. In the 16- and 17-y-old adolescents, the BMI demonstrated low or no correlation with the other methods. Furthermore, it presented disagreements below the diagonal, revealing that the BMI identified fewer obese subjects than the other methods. CONCLUSION: Among the 10- and 11-y-olds, the BMI presented a good correlation with the other methods, independent of ethnicity. The BMI can therefore be used in place of these methods, although it may underestimate obesity. Among the 16- and 17-y-olds, the BMI presented low or no agreement with the other methods, suggesting that it is probably not a suitable index for this age-group in studies focusing on the identification of obesity. In such cases the choice of one of the other methods, depending on availability, cost or technical experience, may represent a better approach.     

Child temperament does not predict adolescent body composition in girls

OBJECTIVES: Our previous cross-sectional analysis of MIT Growth and Development (MIT) Study girls showed that activity temperament, as assessed by a nine-item temperament questionnaire, was related to body composition and nonresting energy expenditure (NREE). In girls with lower levels of physical activity, having a high activity temperament was associated with a higher NREE. Percentage body fat was lower in girls with high vs low activity temperament. Based on these results, we hypothesized that, especially in girls with declining levels of physical activity over adolescence, high activity temperament in childhood would be protective against increased adiposity during adolescence. We tested this hypothesis with longitudinal data from the MIT study. DESIGN, SETTING, AND PARTICIPANTS: A total of 196 nonobese premenarcheal girls 8-12 y old were enrolled between 1990 and 1993. Girls were followed until 4 y postmenarche; average duration of follow-up was 7 y. MEASURES: Activity temperament was assessed at baseline by the girls' mothers with questions modified from those developed by Thomas and Chess that tapped predilection for movement. Temperament, the stylistic component of behavior, is considered relatively stable within an individual. Body composition was assessed by total body water at baseline and study completion (4 y postmenarche), and by bioelectrical impedance (BIA) annually. Physical activity was assessed annually by questionnaire, and by activity diary at baseline only. RESULTS: Child activity temperament was not associated with percentage body fat at 4 y postmenarche in multivariate regression models controlling for baseline percentage body fat, physical activity, parental obesity status, age at menarche, age at baseline, and race-ethnicity. Body composition of girls with low and high activity temperaments who reported declining levels of physical activity over adolescence was not statistically significantly different at study completion. In longitudinal models of percentage body fat by BIA, high activity temperament was not associated with lower adiposity. CONCLUSION: Although high activity temperament was associated cross-sectionally with lower percentage body fat and higher NREE, we did not find evidence to support our hypothesis that high child activity temperament would be protective for increased adiposity prospectively in our cohort of girls followed over the adolescent period.     

Hormonal determinants of regional body composition in adolescent girls with anorexia nervosa and controls

We have previously demonstrated that girls with anorexia nervosa (AN) have higher levels of GH and cortisol and lower levels of estradiol than healthy adolescents. The effects of endocrine alterations on regional body composition in AN, however, have not been reported. We, therefore, enrolled 23 adolescent girls with AN and 20 healthy girls of comparable maturity in a study examining regional body composition. Levels of estradiol and IGF-I, as well as measures of GH and cortisol concentration (using cluster analysis of data obtained from frequent sampling q30' for 12 h overnight) were examined to determine hormonal determinants of regional body composition in adolescent girls with AN and controls. Girls with AN were followed for 1 yr and examined again at weight recovery (10% increase in body mass index) (n = 11). Percent trunk fat and trunk to extremity fat ratio (T/E fat) were significantly reduced in girls with AN compared with healthy adolescents (P = 0.001 and 0.01, respectively). Percent trunk lean mass and trunk to extremity lean mass ratio (T/E lean) were higher in AN than in controls (P = 0.01 and 0.009); percent extremity lean mass was lower in AN (P = 0.009). In healthy controls, total area under the curve (AUC) for GH correlated inversely with percent trunk fat and T/E fat (r = -0.66, P = 0.002 and r = -0.62, P = 0.003). Similar correlations were observed between other measures of GH concentration (mean and nadir) and percent trunk fat and T/E fat. No relationship was observed between GH concentration and regional lean mass or between cortisol concentration and regional body composition. In contrast, GH concentration did not predict regional body composition in adolescents with AN on regression analysis. However, nadir cortisol concentration correlated inversely with percent extremity lean mass (r = -0.49; P = 0.02) and positively with percent trunk lean mass and T/E lean (r = 0.48, P = 0.03; and r = 0.49, P = 0.02) in girls with AN. A similar trend was observed between other measures of cortisol concentration (mean cortisol and AUC) and percent trunk lean mass and T/E lean in AN. Trunk fat was lowest in girls with AN who had high GH but low cortisol levels (based on median values), whereas some preservation of trunk fat was observed in girls with low GH and high cortisol levels. Weight recovery occurred in seven of 11 girls with low GH and high cortisol values; however, only two of the nine girls with high GH and low cortisol recovered weight. High GH with lower cortisol levels may thus be a marker of greater severity of AN. Our results suggest that in healthy controls, GH concentration predicts regional body composition and favors a redistribution of body fat such that T/E fat ratio decreases. In AN, however, high levels of GH and cortisol have contrasting associations with fat mass. High cortisol levels in AN predict a redistribution of lean body mass such that extremity lean mass decreases. Further studies are necessary to better understand the implications of these data.     

女童婴儿期体重增加可预示儿童期体脂量和月经初潮年龄

儿童肥胖的发病率正在不断上升.对英国Wirral的50455名3～4岁儿童的数据资料进行的分析显示,在1998至2003年间,他们的平均体重指数(BMI)和超重风险均稳步上升.研究表明儿童期肥胖可影响成年后的健康状况,并可预示以后心血管疾病的发生和死亡率.因此,在婴儿早期即开始干预可能有助于预防肥胖及与之相关的代谢异常.     

Early menarche and the development of cardiovascular disease risk factors in adolescent girls: the Fels Longitudinal Study

The purpose of this study was to evaluate the influence of menarcheal age on changes in insulin, glucose, lipids, and blood pressure during adolescence and to assess whether body composition modifies this relationship. We examined 391 girls, a subset of Fels Longitudinal Study female participants (8-21 yr of age). Self-reported menarcheal age was classified based on the National Health and Nutrition Examination Survey III distribution, in which early menarche was at the 25th percentile or less (11.9 yr). Age at menarche was examined in relation to measures of body composition [e.g. fat-free mass (FFM) and percent body fat (PBF)], insulin resistance, blood pressure, and lipid profile. The effects of menarcheal age and body composition on cardiovascular disease risk factor changes were analyzed with serial data mixed models. Median menarcheal age was 12.7 yr (range, 9.8-17.0 yr), with 91 girls (23%) classified as early menarche. Girls with early menarche had more deleterious changes in insulin, glucose, blood pressure, FFM, and PBF levels than girls with average or late menarche. Menarcheal age adversely affected cardiovascular disease risk factor changes independent of age and changes in FFM or PBF. Girls with early menarche exhibited elevated blood pressure and glucose intolerance compared with later maturing girls, independent of body composition.     

The effect of the media on body satisfaction in adolescent girls

It has been suggested that the media, in consistently portraying thin, stereotypically attractive bodies, exacerbates the phenomenon of body dissatisfaction, and in consequence may be partly responsible for the increase in the prevalence of eating disorders. A recent study by Ogden and Mundray (1996) observed that an acute exposure to such images increased the body image dissatisfaction of adult subjects, whilst exposure to images of overweight individuals ameliorated dissatisfaction. The present study attempted to investigate this effect in adolescent girls. The results failed to support the experimental hypothesis, however possible reasons for this are discussed. It is suggested that the media's influence on individuals' self‐evaluations may be more complex than Ogden and Mundray's results imply, differentially affecting individuals' levels of satisfaction. Copyright © 1999 John Wiley & Sons, Ltd and Eating Disorders Association.     

Body composition in adolescent girls with type 1 diabetes.

AIMS: To compare body composition in adolescent girls with Type 1 diabetes with healthy controls. RESEARCH DESIGN AND METHODS: In this population-based study, body composition was examined, using dual-energy X-ray absorptiometry (DXA) and skinfold measurements, in 18 adolescent post-menarcheal females, 16-19 years of age, with Type 1 diabetes since childhood in comparison to age-matched healthy control subjects. RESULTS: Body mass index was 2.7 kg/m2 higher in diabetic patients (26.3 +/- 2.6 vs. 23.6 +/- 3.8; P < 0.05). The overweight consisted almost entirely of increased fat mass, as evaluated by both skinfold measurements and DXA. Bone mineral density did not differ between the two groups. In diabetic females, the distribution of the fat mass was increased in the upper part of the body. The fat distribution, expressed as the abdominal-to-leg ratio, was significantly correlated to glycated haemoglobin (HbA1c) (r = 0.69; P < 0.005), daily dosage of insulin expressed per kilogram body weight (r = 0.78; P < 0.0005) and total cholesterol (r = 0.60; P < 0.001). CONCLUSIONS: The observed overweight in adolescent females with Type 1 diabetes is explained by an increased fat mass. Abdominal fat accumulation was associated with poor glycaemic control, increased need for insulin and elevated blood lipids.     

Anthropometry and body composition in persons over 60. The importance of physical activity

OBJECTIVE: To measure anthropometric indicators of body composition by electric bioimpedence, as well as physical activity, blood glucose and arterial pressure in rural people over 60 years of age. MATERIAL AND METHODS: A total of 54 subjects over 60 years old were selected by intentional non-probabilistic sampling. They were subjected to a standardized protocol to measure anthropometric indicators, body composition by electric bioimpedance (EBI), and physical activity was determined by an activity questionnaire. Arterial pressure and glucose tolerance levels were also measured. Analysis included Student's t test to detect differences by sex and the association of physical activity, body composition and other variables by simple linear regression and Pearson's correlation coefficient. RESULTS: Physical activity correlated negatively with percent fat (r = -0.36; p = 0.007) and diastolic (r = -0.36; p = 0.006) and systolic blood pressure (r = -0.32; p = 0.018), and body mass index with post dose glucose (r = 0.31; p = 0.024). CONCLUSIONS: Physical activity in this age group may have a favorable impact with respect to the mentioned health indicators.     

Estimation of body fat in Caucasian and African-American girls: total-body electrical conductivity methodology versus a four-component model

BACKGROUND: Obesity has been increasing dramatically in recent years among children, particularly African-American girls. Total-body electrical conductivity (TOBEC) is a simple way to measure body fat with minimal risk. OBJECTIVE: This study compared the agreement between the percentage of fat mass (%FM) predicted using two TOBEC equations with %FM measured by a four-component model in 73 Caucasian and 41 African-American girls. DESIGN AND MEASUREMENTS: %FM predicted using the TOBEC equations was compared with %FM from the four-component model based on measurements of body density, body water and bone mineral content. RESULTS: Analyses by linear regression analysis and by the Bland and Altman methods comparison procedure showed that the equation using the square root of the TOBEC zero-order Fourier coefficient and the subject's height yielded more accurate and more reproducible %FM, regardless of race, than the TOBEC linear equation, which was based on the zero-, first- and second-order Fourier coefficients. The Bland and Altman comparison further revealed that the accuracy and limits of agreement of the TOBEC linear equation were related to body fatness among the Caucasian girls. The relationship, however, disappeared when prepubescent girls and a girl with low %FM were excluded from the analysis. CONCLUSIONS: The TOBEC square root equation with adjustment for body geometry and length is recommended for use in adolescent girls, as it yielded better agreement with the criterion method. However, further validation of the TOBEC instrumentation for estimating body fat in prepubescent children and children with low body fat is warranted.     

Onset of ovulation after menarche in girls: a longitudinal study

INTRODUCTION: Hypothalamic-pituitary axis maturity has been believed to be the rate-limiting step in the development of ovulatory menstrual cycles. We hypothesized that, given current nutritional conditions, hypothalamic-pituitary axis maturation would be relatively rapid in menarcheal girls. METHODS: Daily urine and menstrual records were collected for 2 yr each from 10 girls aged 11-13 yr at study entry. Urinary excretion of LH, FSH, estradiol (E1c), and progesterone (Pdg) metabolites was measured using established ELISAs. An objective algorithm detected rises of LH, FSH, E1c, and Pdg consistent with follicular maturation and/or ovulation. RESULTS: Nine of 10 girls enrolled into the study experienced the onset of menarche prior to or during the 2-yr collection period. LH and FSH surges, as well as small amplitude Pdg increments, were observed prior to menarche. Regular, ovulatory-appearing cycles with LH surges and gradually increasing and more sustained Pdg rises were observed over time after menarche, although duration of Pdg elevations remained shorter than in adult women (8.9 +/- 1.0 vs. 12.1 +/- 0.8 d, P = 0.043). E1c levels leading to LH/FSH surges were lower in perimenarcheal girls than adult controls, and bleeding episodes did not uniformly correlate with hormone patterns. Progressive increases in FSH and Pdg, but not LH or E1c, were observed in association with menarche. CONCLUSION: Mature hormone patterns are established within several months of and even prior to menarche in normal-weight perimenarcheal girls. Factors determining menstrual bleeding in perimenarcheal girls may not be solely dependent on reproductive hormones or the neuroendocrine axis.     

Twenty-four hour growth hormone and leptin secretion in active postpubertal adolescent girls: impact of fitness, fatness, and age at menarche

CONTEXT: GH is strongly related to body composition, physical activity, and pubertal progression. Adolescent girls decrease physical activity during puberty, whereas their weight increases. Because leptin is a good index of energy balance in active young women, we hypothesized that leptin is related to GH secretion in this population while taking into account fitness, fatness, and age at menarche. METHODS: We measured body composition and maximal oxygen consumption (VO(2)max) in 37 postpubertal adolescent girls aged 16-21 yr. GH was sampled every 10 min and leptin hourly for 24 h. We first analyzed 6-h time blocks by repeated measures for GH and leptin, with body mass index (BMI), percent body fat, and VO(2)max as covariates for the entire group and a lean subgroup. The deconvolution method was used to characterize GH pulsatility from individual time points. RESULTS: GH varied through the day (P < 0.0001), with the highest concentrations overnight. BMI, percent body fat, and VO(2)max were related to GH concentrations in the entire group, whereas leptin predicted GH in the entire group as well as the lean subgroup of girls. Higher leptin was related to lower GH concentrations (P = 0.011), regardless of time. A log leptin level increase by 1 unit decreased GH by 27%. Pulsatility characteristics showed a 1-yr increase of age at menarche increasing total GH input by 20% (P = 0.0035) independently from BMI. CONCLUSION: In postpubertal adolescent girls, leptin is related to GH concentration across the lean to overweight BMI spectrum. GH pulsatile secretion was greater in girls with later age at menarche.     

Percent body fat measured by BIA and DEXA in obese, African-American adolescent girls

OBJECTIVE: To compare the estimation of body fat between bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DEXA) in overweight, African-American female adolescents. SUBJECTS: In total, 54 African-American adolescent female subjects were recruited for Study 1. Each adolescent's body mass index was greater than the 85th percentile and their average body fat was 45% according to DEXA. A total of 26 African-American adolescent female subjects were available for Study 2, and had an average body fat of 26% according to DEXA. MEASUREMENTS: Percent body fat was measured by DEXA and BIA. Seven different BIA equations were tested. Both sets of data were analyzed using Bland-Altman regression analyses, utilizing percent body fat measured by DEXA as the criterion. RESULTS: The Kushner equation provided estimates that were unaffected by body fat in both studies. Estimates were unbiased when applied to the exclusively overweight sample and biased when utilized with the separate sample of normal weight and obese girls. The remaining equations were biased, provided inconsistent estimates across body weight, or were biased and provided inconsistent estimates. Ethnicity-specific and ethnicity-combined equations performed similarly in the obese sample, but became more disparate when applied to a sample encompassing a wider body weight range. The limits of agreement between all BIA equations and the DEXA estimates ranged from 6 to 9%. CONCLUSION: The study suggests that the Kushner BIA equation is appropriate for use with African-American female adolescents across the weight spectrum, while the majority of BIA equations underestimated percent body fat as body fat increased.     

The relationship between body fat distribution and weight loss in obese adolescent girls.

Recent studies have demonstrated an association between the pattern of body fat distribution and the occurrence of cardiovascular risk factors. In this study, we evaluated changes in body fat distribution as defined by several anthropometric criteria during a six week weight reduction programme in 110 obese adolescent girls (mean age 15.2 +/- 0.4 years). The standardized regimen included a mixed diet of 1032 kcal/day and a daily exercise programme of 1-2 h duration. The mean weight loss was 8.6 +/- 2.8 kg, decreasing the body mass index (BMI) from 31.4 +/- 4.7 to 28.2 +/- 4.9 kg/m2 (P < 0.01). The reduction in body weight was accompanied by a significant decrease in the waist-to-hip ratio (WHR) from 0.86 +/- 0.06 to 0.81 +/- 0.05 (P < 0.01). The initial WHR was correlated with the degree of weight loss independent of the initial weight (r = 0.34, P < 0.001). Categorized according to the waist-to-hip ratio girls in the upper tertile (WHR > 0.88) lost significantly more weight than girls in the lower tertile (WHR < 0.80) (9.8 +/- 2.7 vs. 6.8 +/- 2.5 kg, P < 0.01). These findings suggest that girls with an abdominal type of obesity benefit more from a weight reduction programme than girls with a gluteal-femoral type of obesity.     

The influence of significant others on disordered eating and body dissatisfaction among early adolescent girls

The current study evaluated the variables associated with disordered eating and body dissatisfaction among early adolescent girls. The impact of the following variables on body dissatisfaction and disordered eating were assessed: perceived views of society, parents and peers regarding weight, self esteem, locus of control, onset of menarche, body mass index and the importance placed on appearance. One hundred and eleven girls enrolled in year 7, aged between 11 to 13 years (x=12.46) participated in this study. The results indicated that young adolescent girls expressed moderate levels of disordered eating and moderate dissatisfaction with their bodies. Respondents who were more dissatisfied with their bodies exhibited higher levels of disordered eating. The most important predictors of body dissatisfaction were self esteem, body mass index, and the perceived views of society. Prediction of disordered eating was not improved by the perceived views of significant others, after the other variables were accounted for. Limitations and direction of future research are discussed. Copyright © 2000 John Wiley & Sons, Ltd and Eating Disorders Association.     

Resting metabolic rate and body composition of Pima Indian and Caucasian children.

Since a low metabolic rate (for a given body size and body composition) is a risk factor for body weight gain and obesity is prevalent among Pima Indians, we have tested whether Pima Indian children have a low resting metabolic rate (RMR) as compared to Caucasian children. Body composition (bioelectrical resistance) and RMR were measured in 43 Pima Indian children (22 male/21 female, mean +/- s.d. 9.9 +/- 1.1 years) and 42 Caucasian children (21 male/21 female, 9.7 +/- 1.2 years). Pima children were taller (143 +/- 9 vs. 137 +/- 8 cm, P less than 0.001), heavier (48.6 +/- 15.8 vs. 32.9 +/- 7.8 kg, P less than 0.001) and fatter (39 +/- 10 vs. 24 +/- 7% fat, P less than 0.001) than Caucasians. Absolute values of RMR were higher in Pimas than in Caucasians (6234 +/- 1201 vs. 5171 +/- 715 kJ/day, P less than 0.001), but similar when adjusted for differences in body size, body composition and sex. Contrary to our hypothesis, we did not find a decreased RMR in Pima children when compared to Caucasian children. Therefore, the high prevalence of obesity in Pima children at age 10 suggests that excess energy intake and/or low levels of physical activity might be the major aetiological factor. However, this study does not exclude the possibility that a low metabolic rate might be a predisposing factor at an earlier age.     

The effect of oxandrolone on body proportions and body composition in growth hormone‐treated girls with Turner syndrome

Objective Untreated girls with Turner syndrome (TS) have short stature, relatively broad shoulders, a broad pelvis, short legs, a high fat mass and low muscle mass. Our objective was to assess the effect of the weak androgen oxandrolone (Ox) on body proportions and composition in growth hormone (GH)‐treated girls with TS. Design/Patients 133 patients were included in a randomized, placebo‐controlled, double‐blind study. Methods Patients were treated with GH (1·33 mg/m² per day) from baseline, combined with placebo (Pl) or Ox in a low (0·03 mg/kg per day) or previously conventional (0·06 mg/kg per day) dose from the age of eight, and oestrogens from the age of twelve. Sitting height, biacromial and biiliacal distances compared with height (i.e. shape values), BMI, waist circumference, sum of 4 skinfolds (sum4skin) and upper arm muscle area (UAMA) SD scores (SDS) were assessed half‐yearly. Results Compared with GH + Pl, adult shape values on GH + Ox tended to be higher for sitting height (Ox 0·03, P = 0·2; Ox 0·06, P = 0·02) and biacromial distance (Ox 0·03, P = 0·2; Ox 0·06, P = 0·07) and lower for biiliacal distance (Ox 0·03, P = 0·004; Ox 0·06, P = 0·08). Sum4skin SDS tended to decrease more (Ox 0·03, P = 0·2; Ox 0·06, P = 0·005) while UAMA SDS increased more (Ox 0·03, P < 0·001; Ox 0·06, P < 0·001) than on GH + Pl. The increase in BMI and waist circumference SDS was comparable between the dosage groups. Conclusions In GH‐treated girls with TS, Ox 0·06 increases sitting height and tends to increase biacromial distance and decrease biiliacal distance, while Ox 0·03 significantly decreases biiliacal distance compared with height. Furthermore, Ox 0·06 reduces subcutaneous fat mass, and both Ox dosages increase muscle mass.     

Bone metabolism and body composition in Japanese patients with active acromegaly

OBJECTIVE: To assess prospectively the effects of low dose oestradiol on arterial endothelial and smooth muscle function in healthy men. Oestrogen use is associated with reduced cardiovascular disease in oestrogen-deficient women, however, the vascular effects of low-dose oestradiol in healthy men have not been investigated previously. PATIENTS AND DESIGN: Twenty-three men (aged 32 +/- 8 years) were randomized to receive depot implants of testosterone (T) alone (group 1, n = 10), or T with either 10 mg (group 2, n = 7) or 20 mg (group 3, n = 6) of oestradiol (E). MEASUREMENTS: Hormone levels, lipids and vascular reactivity were measured before, 1 month and 6 months after hormone implantation. Using high-resolution ultrasound, brachial artery diameter was measured at rest, during reactive hyperaemia (leading to flow-mediated dilatation, FMD, which is endothelium-dependent) and after sublingual nitroglycerin (GTN, an endothelium-independent dilator). RESULTS: Oestradiol produced a dose-dependent increase in plasma oestradiol (at 1 month 96 +/- 7, 149 +/- 6, 192 +/- 23 pmol/l in the 3 groups, respectively, P < 0.001 by ANOVA for trend). Minor side-effects (gynaecomastia, nipple tenderness) indicated that 20 mg oestradiol was the maximum tolerated dose. There was also a dose-dependent increase in FMD with oestradiol dose: at 1 month, - 0.2, + 0.2 and + 1.8% for groups 1-3, respectively (P = 0.31 by ANOVA for trend); and at 6 months, - 0.8, + 0.4 and + 2.2% (P = 0.02). The rise in oestradiol levels following treatment correlated with the improvement in FMD (P = 0.01). GTN responses were similar in the 3 groups throughout the study. CONCLUSION: In healthy young men, oestradiol supplementation is associated with enhanced arterial endothelial function, a key marker of vascular health.     

Impact of fatness, fitness, and ethnicity on the relationship of nocturnal ghrelin to 24-hour luteinizing hormone concentrations in adolescent girls

CONTEXT: Ghrelin is related to energy balance that regulates food intake. OBJECTIVE: The aim was to explore whether ghrelin would be linked to differences in fitness in adolescent girls, whose menstrual cycles are sensitive to changes in energy balance. METHODS: A total of 72 girls, ages 14-21 yr, including five with amenorrhea, were studied in the follicular phase. LH was sampled every 10 min over 24-h, and ghrelin was measured hourly between 2300 and 0300 h. Body composition was measured by dual x-ray absorptiometry. Fitness was characterized by reported frequency of exercise per week and by maximal oxygen consumption with "high" vs. "low" fitness groups defined from maximal oxygen consumption norms for this population. Data were analyzed with SAS software (SAS Institute Inc., Cary, NC). RESULTS: Ghrelin was related to percent body fat (P = 0.038; R(2) 0.07), weekly exercise (P = 0.032; R(2) 0.07), and 24-h mean LH (P = 0.002; R(2) 0.13). The ghrelin relationship with LH was more pronounced in the low-fitness group. In multiple regression models, 24-h LH was an independent predictor of ghrelin after adjusting for percent body fat, fitness, exercise, or age. Ghrelin was higher in Caucasian girls than in African-American girls after adjusting for covariates at 0200 h (P = 0.017). CONCLUSIONS: Twenty-four-hour LH is an independent predictor of nighttime ghrelin concentrations in postpubertal adolescent girls. Diverging patterns in ghrelin may reflect differences in exercise patterns and/or may be influenced by ethnicity. These data introduce ghrelin as a biomarker of individual differences in energy balance during the menstrual cycle and across ethnicities.